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[Not-Fixed] How to install new Z3 D6603 LTE on AT&T network

[Not Fixed] see bottom of this post.
It is fairly easy to install a new D6603 to work completly on the AT&T network. It is not so easy to find the answer of how to do it in the threads and posts. I tried many suggestions and wasted a lot of time. Hopefully this will save you from that fate.
First you must know that you can't use the IMEI number of your new phone if you want it to work completly as it should. If you use the Z3 IMEI you will have trouble with data of various sorts and the phone will go off line when on LTE after 20 or 30 minutes and you will not receive calls or SMS messages. I do not know why but it has been suggested that the AT&T network does not recognise this phone so it causes trouble.
If you have an AT&T nano-sim from your old phone then just put it in the phone. (Cut downs work but can cause other problems some say.) When the SIM is inserted for the first time into a new phone there is a prompt that asks if you want to download the APN. Hit 'yes' and the phone downloads the APN itself.
If it does not ask then go to Settings>More>Mobile Networks>Prefered Network Type and be sure LTE (Preferred) is selected. Then connect your phone to the internet and then go to Settings>More>Internet Settings and select AT&T. You should be good to go.
If you need to get a nano-sim then go to the AT&T store or call and they will give you one or send you one for free. You will need to use the IMEI number from a LTE phone that is already on the AT&T system. You can use your old phone or borrow the number from someone. If the rep installs the sim in the Z3 with the 6603 IMEI don't worry. Just call support later and tell them you sent your new phone back and want to go back to your old IMEI or have a new IMEI (from an existing AT&T phone). They will enter it and off you go. The phone from the IMEI will show in the picture on your account page. Big deal!
Update: This worked for hours last night but this morning it is back to not receiving calls. Simply turning wifi off and it began to receive calls as GPRS was switched back on. My wifi was on which has been said to cause problems. I will test with wifi off and report back. Had "no service" instead of AT&T on upper left of lock screen. A full shut down for several minutes than re-boot solved that.

YMMV. I've been on ATT with a Z3 purchased from Sony store for several months and it was registered in an ATT store by scanning the IMEI off the box followed by updating Internet settings in Setup. ATT online shows unknown model but everything works including LTE and MMS. There is something else involved when problems like this occur probably some setting not getting reset. I registered the Z3 on a new line with a new Sim card because I wanted to take my time moving stuff off my old phone--this may have avoided the problems.

JudH said:
YMMV. I've been on ATT with a Z3 purchased from Sony store for several months and it was registered in an ATT store by scanning the IMEI off the box followed by updating Internet settings in Setup. ATT online shows unknown model but everything works including LTE and MMS. There is something else involved when problems like this occur probably some setting not getting reset. I registered the Z3 on a new line with a new Sim card because I wanted to take my time moving stuff off my old phone--this may have avoided the problems.
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I've also had no problems with my Z3 on AT&T. Works great, receives sms/mms immediately, etc..

esheesle said:
I've also had no problems with my Z3 on AT&T. Works great, receives sms/mms immediately, etc..
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Click to collapse
AT&T's system sometimes takes a while to get updated with new IMEIs that trigger LTE provisioning for a users' account.
Once your account is provisioned for LTE you never have to worry about it again, but sometimes if you have a phone the system doesn't recognize, it is a pain to get AT&T to properly provision your account. Supposedly properly trained in-store reps can do it - the key being "properly trained" - Never try to do anything "unusual" by calling AT&T customer service, and NEVER use a franchise/kiosk in-person for service - make sure you're at a corporate-owned store! Even then, some stores might have incompetent staff. I've been lucky that all of my local corporate stores are pretty well staffed.

So you are saying that your Z3's with wifi and LTE on with AT&T are working as they should?
With LTE off my phone responds normally with wifi on. With LTE and wifi on it will not respond to calls after a 30 minute sleep. It does not show missed calls. Calls go straight to voice mail after 2 rings. Could you tell me what level your LTE dBm's are? Thanks!

I was told not to give them my imie# but, after recvng the minisim I had to call them in order to 'provision' it to work at all and they needed that #. I have never had any problems personally and am assuming this may be because you gave them the wrong #. Again I am only guessing. Oth, if I had had a different imie to give, I would have done so myself.

It is very strange and I am feeling it is more signal strength related than how you provision your phone. (Once it is provisioned correctly.) It seems that more people have less problems when they already have a nano-sim and just plunk it in the new phone. This might indicate that they already had a strong signal from the get go. My old HTC One + get's a better signal than the Sony in the same locations with the same (new) SIM. With the Devilcase bumper on it gets 5% less. My very limited tests yesterday seemed to indicate that it was signal strength related. I am not enough of a conspiracy theorist to imagine that AT&T would program their system to not function correctly with sims that are provisioned with these Sony phones which they are obviously ignoring for some reason. Or am I?

I had all kinds of problems with the Z3 on AT&T. The IMEI caused an issue since AT&T linked it to a flip phone and therefore couldn't provision LTE. I changed it to an old AT&T LTE device and then I was able to get LTE but was having the same issue with calls going directly to voicemail and texts showing up hours later in bunches. I found the solution was to switch off LTE in the quick settings menu. All calls and texts came through and on time while LTE was off. If I needed a data boost to stream, I turned it back on until I was finished streaming. This was while on KitKat. After upgrading to Lollipop, I was able to keep LTE turned on and calls and texts still arrived on time.

I use data rarely. Mostly wifi. If I don't leave LTE on, my phone reverts to wcdma preferred. And why can't LTE just work without me having to constantly turn it back on? What bugs me is having the APN settings greyed out. I want to be able to turn it off. If anything it seems the phone itself is preventing me from accessing the sim. It feels like I'm borrowing something which contains lots of MY private data. I know my phonebook is stored locally but I also noticed there is no option of specifying the sim or not. Anybody know how to switch APN on and off? In fact, overall even rooted, I still feel like I have almost no power over it. I can't even disable the cellular connection without going full on airplane mode and I do not trust that. I don't even fly so that needs work for sure. Dumb question but could I buy a working nanosim from say 7-eleven that my apn switch will work with?

"Anybody know how to switch APN on and off?"
On my Z3 on OTA stock Lollypop I have an icon in quick settings to turn LTE on and off. Drag two fingers down from the top of the screen. If no LTE icon then select the pencil icon at the top and select the LTE icon. There is also a mobile data icon switch there.
To turn off your radio completly you can get the Advanced Signal Status app and select additional info at the bottom and click phone information and turn off radio. Probably a number of ways to do it but that is one.
Sim contact storage was a way to move information from phone to phone. You can still do it but not really necessary with cloud backup and storage. Google does it for me without me having to do anything which I like. I still save contacts to the sim just because I can. Export and import in your contacts app menu.

johnboatcat said:
So you are saying that your Z3's with wifi and LTE on with AT&T are working as they should?
With LTE off my phone responds normally with wifi on. With LTE and wifi on it will not respond to calls after a 30 minute sleep. It does not show missed calls. Calls go straight to voice mail after 2 rings. Could you tell me what level your LTE dBm's are? Thanks!
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Click to collapse
Works fine here. I don't pay attention to the dBm estimates since these aren't measured with calibrated test equipment and vary widely. Those numbers are basically worthless.
The only valid comparison is data performance in a given environment (ideally a difficult weak-signal one) - and at my desk with very weak signal, every phone I've ever used performs similarly to the Z3.

"Those numbers are basically worthless."
True, but we have narrowed this down to the possibility that it might be signal related so it is worth a shot. If people whose phones are working fine would measure the LTE dBm on Advanced Signal Status at the location where their phone sits and works well the most we might possibly see some measure of difference in the phones that are not working. Most of the non-working phones seem to work sometimes so signal strength is the next best parameter to rule out. Thanks!
Here are the screen shots of my phone with LTE on, LTE and wi-fi and LTE off and wi-fi.
How do the working phones compare? Does your CDMA (voice) also go to 0% when LTE is on and GSM = n/a?

Thanks. I think adv sig nfo actually works. I'm amazed actually. I can't find the phone's native greyed out apn switch anyways which really makes no sense.

How do you activate wi-fi calling?

Does anyone know how to activate wi-fi calling on the Z5? I figured it'd be a menu setting, but I can't find it. I'm using the Taiwan version of the Compact and am using MetroPCS here in the States.
Thanks.

To answer my own question. It appears that wi-fi calling is only available with some carrier phones. So for instance, EE in England says on their setup page,
"WiFi Calling is only available on the EE version of the Sony Xperia Z5 Compact, bought directly from us in one of our stores, online at EE.co.uk, through our telesales team, or through corporate sales if you are a corporate customer."
So, I guess my question now is, is there a way to flash the phone so that I can get this feature on my non-EE phone? My carrier, MetroPCS, does allow wi-fi calling, but they don't sell the Z5 (and likely won't ever sell it).

You can try flashing the EE ROM with flashtool and see if you have that option. You will get carrier specific bloatware as well.

Would I be able to delete the bloatware? And I'm new to Android. When I flash, does it delete all of my settings and downloads and whatnot? I'm assuming I can back them up someplace in case it does, but like I say, I'm new to this. Also, where would I get the EE Rom from?

Look for Xperifirm. Download and install. You can get the firmware there. Next download flashtool version 0.9.19.10. You can bundle the firmware files into a ftf and flash, both with flashtool. Read the respective guides. To keep data, look at options when flashing and choose not to wipe user data. I would type it up but the instructions are on XDA, just search.

Neither WiFi calling or VoLTE will not work on the Sony Z5 unless your carrier/network offers the Sony Z5 for sale directly.
Note, WiFi Calling and VoLTE are two separate features but similar network functions on the operators side.
Note, MetroPCS is a sub-brand of the T-Mobile USA network so Metro is pretty much TMo USA.
Since T-Mobile USA does not offer the Z5 you will not be able to get WiFi calling working. In order for WiFi Calling or VoLTE to be supported the network operator must customize the ROM to include the WiFi calling and/or VoLTE network configurations. Unlike the typical SIM card and APN settings which are industry standard and can be adjusted manually. WiFi calling and VoLTE are somewhat more complex and include carrier/network specific security certificates to work. Apple can get away with supporting WiFi calling and VoLTE simply by swapping SIMs because the T-Mobile configs are loaded into their core iOS software which goes out to everyone around the world. (Probaly one of the reasons the iOS eats up so much storage...but i digress) Android runs much leaner and does not carry all the extra configs for all global networks...hence a carrier (i.e. T-Mo US) tweaked version of the Z5 ROM would be required for this all to work.
If T-Mobile USA offers the Z5 in the future you may be able to unlock the boot-loader and flash the T-Mobile specific ROM onto your phone and get WiFi Calling and VoLTE to work. But if T-Mo USA never offers the Z5 then you will never have WiFi calling supported.
Hope that helps....
WiFi calling and VoLTE are pretty much the same thing...just VoIP. And in most operators case WiFi Calling and VoLTE are the same back end network call processing systems. VoLTE is easier for the operator to secure as the customer is using the operators LTE and IP network. WiFi calling is seen on fewer operators as it requires more security since you can access the operators network from any public or private IP network.
---------- Post added at 10:28 PM ---------- Previous post was at 10:20 PM ----------
and in theory you could extract the WiFi calling stack form the EE network's Z5 ROM and load it into a custom ROM. That would give you the software capability to support WiFi calling....But you will still need the T-Mobile USA WiFi calling fqdn for the WiFi border controller and their security certificates which are typically specific to a handset model. And again since TMo does not offer the Z5 there are no Z5 certificates.

Ah, well that sucks.

Yeah I feel ya, I love WiFi calling too

Some network providers have their own apps to allow it. Like in the UK, O2 network has an app called TU go

All hope isn't lost - Android M is supposed to have a provision for wifi calling. I've read posts of people with Nexus 6's on M (google play editions, so no carrier specific models) that have been able to use wifi calling. The current loss of band 12 (hoping this will change too) as well as the loss of wifi calling as a fallback has been the only drawback to this otherwise excellent handset. I absolutely love the thing. It just works, no fuss.

I know this isn't helpful, especially for those outside of the US, but this is why I ported my number to google voice a long time ago. VOIP works great over Wifi for me most of the time and when I have LTE reception, I can still use Voip albeit with increased data consumption.

shizenyasuya said:
I know this isn't helpful, especially for those outside of the US, but this is why I ported my number to google voice a long time ago. VOIP works great over Wifi for me most of the time and when I have LTE reception, I can still use Voip albeit with increased data consumption.
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Do you know of any guides for how this is supposed to work? I have Google Voice, and I have Hangouts, but I'm not sure how they're supposed to work in tandem for wi-fi calling. Would I be forced to actually open up the Google Voice app in order to make wi-fi calls? How is that any different from something like Talkatone?

Adrift98 said:
Do you know of any guides for how this is supposed to work? I have Google Voice, and I have Hangouts, but I'm not sure how they're supposed to work in tandem for wi-fi calling. Would I be forced to actually open up the Google Voice app in order to make wi-fi calls? How is that any different from something like Talkatone?
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Yeah, that's a bit of a pain in the ar$3. I install google voice and hangouts on any phone/tablet I get, Google voice is necessary to route all outgoing calls through GV so that my GV number shows up on my call partner's caller ID. (even though you can dial directly from the native phone dialer) I install Hangouts to manage sms and google talk (now just google hangouts but specified to avoid... or contribute to, (as the case may be) confusion) messages. You can also dial directly from Google Hangouts (this is the only option when you're only using Wifi, without cellular signal) So my thought flow kinda goes like this.
To make a call:
1)check for cell signal, if there is signal, use the native dialer to place a call
2) if there is only WiFi, use hangouts (or hangouts dialer) to place a call
Receiving calls: (If you need help I can tell you the specific settings)
1)when the phone rings, determine if it's ringing via Hangouts or the native phone app
2) check for cellular signal and wifi signal
3) if cell signal is 2g only, only answer with the native phone app (sometimes hangouts will ring first) and I have to wait for the native phone app to realize there is a call coming in (forwarded of course to my cellular provider number from GV)
4)if connected to WiFi, or I have LTE coverage (sometimes even on 3g) pick up the hangouts ring.
Sometimes I do miss calls because I'm waiting for the native phone app to ring when I'm on 2g, but hangouts rings first and the native phone app doesn't ring, but those instances are fairly infrequent and I can just call them back.
---------- Post added at 04:51 AM ---------- Previous post was at 04:48 AM ----------
Adrift98 said:
Do you know of any guides for how this is supposed to work? I have Google Voice, and I have Hangouts, but I'm not sure how they're supposed to work in tandem for wi-fi calling. Would I be forced to actually open up the Google Voice app in order to make wi-fi calls? How is that any different from something like Talkatone?
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Also, sorry I've never used Talkatone, so I don't know if it works any differently. You don't have to have google voice installed to make / receive wifi calls via hangouts. you just have to have opted in to hangouts on your google voice account. The ONLY reason I still install GV is to make sure that when I make outgoing calls from the native phone app, my GV number shows up on the recipient's caller ID. They should really just bake this into hangouts and completely depreciate the GV app.

You could port the t-mobile wifi calling apps from the z3. I ported wifi calling to my att g2 from the t-mobile rom. It's not really that hard if you know how to read logcats

Many retail mobiles have "Wifi Calling" function but not any menu entry to enable , The APP can check the hidden function and enable it if can use.
https://play.google.com/store/apps/details?id=com.widget7.wifi.calling

VZW WIFI Calling on unlocked Note 20 ultra 5G

Found out the guy lied. So the US unlocked N20U does work with VZW wifi calling.

It definitely does work with my N20U on Verizon.

The only differences between the Unlocked and VZW version are:
1. Native Verizon video calling doesn't work on unlocked, but the integrated Duo video calling is better anyways.
2. Verizon's model doesn't have the Samsung "Smart Call" feature for Caller ID. Instead, it uses Verizon's app.
3. Verizon's version has the Verizon bootscreen and a ton of bloatware, especially games, news apps, and what not. Fortunately, most can be uninstalled, and the rest can be disabled using ADB.

Guyinlaca said:
The only differences between the Unlocked and VZW version are:
1. Native Verizon video calling doesn't work on unlocked, but the integrated Duo video calling is better anyways.
2. Verizon's model doesn't have the Samsung "Smart Call" feature for Caller ID. Instead, it uses Verizon's app.
3. Verizon's version has the Verizon bootscreen and a ton of bloatware, especially games, news apps, and what not. Fortunately, most can be uninstalled, and the rest can be disabled using ADB.
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I can confirm all of the above. I have an unlocked phone, on U1 firmware, with a Verizon SIM. Wifi calling works. There is no "Advanced Calling" menu in Connection Settings, but there's a toggle for VoLTE and it was switched on by default. No 4G icon, but rather a LTE+ icon is shown in status bar. The only thing I haven't found a workaround for is the native video calling. I cannot initiate it (phone app does not show the option when I'm on a call with another Verizon phone) and if another Verizon phone attempts to initiate a native video call, it tells them that I cannot accept video calls. I checked my VZW account settings on a PC, and despite the video call option being on and not blocked, native calling doesn't work, as described above. Duo works fine for video. I was able to get Visual Voicemail by installing the app that I go from another thread. I installed it before checking to see if the U1 firmware added it by default, so I can't say for sure that it wasn't there already.
Sent from my SM-N986U using Tapatalk

So I had an interesting observation. I flashed my Verizon Note 10+ to U1 firmware and noticed a drastic reduction in data speeds. After getting the Note 20 Ultra, I noticed the data speeds were nearly doubled. I then disabled a ton of Verizon and Samsung apps, and my data speeds dropped drastically as well. Through the process of elimination, I found that the "My Verizon Services" app seems to have a major impact on data speeds. As long as I keep that enabled on the Verizon firmware, data speeds are blazing fast.
Is it possible that Verizon uses apps to prioritize or de-prioritize data speeds? I'd be curious if one could do a side by side of the Unlocked vs Verizon firmware.

ferzmedina said:
I can confirm all of the above. I have an unlocked phone, on U1 firmware, with a Verizon SIM. Wifi calling works. There is no "Advanced Calling" menu in Connection Settings, but there's a toggle for VoLTE and it was switched on by default. No 4G icon, but rather a LTE+ icon is shown in status bar. The only thing I haven't found a workaround for is the native video calling. I cannot initiate it (phone app does not show the option when I'm on a call with another Verizon phone) and if another Verizon phone attempts to initiate a native video call, it tells them that I cannot accept video calls. I checked my VZW account settings on a PC, and despite the video call option being on and not blocked, native calling doesn't work, as described above. Duo works fine for video. I was able to get Visual Voicemail by installing the app that I go from another thread. I installed it before checking to see if the U1 firmware added it by default, so I can't say for sure that it wasn't there already.
Sent from my SM-N986U using Tapatalk
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Click to collapse
Thanks for sharing your observations regarding wifi calling. How can one tell it is working? I am used to older phones advising that wifi calling was in use via text in the phone app. I'm not seeing this notification on my new unlocked T-Mobile-branded N20U with Verizon SIM.
I also noticed the VoLTE toggle in the phone app, switched on and greyed-out, can't be deselected. Of course they don't want to support anything but VoIP anymore. What is the behavior, if the cell signal is decent it won't use wifi? It can't be forced to prefer wifi, can it? I used the trick of putting it in airplane mode, then turn on wifi to try and force it to wifi call. It said it couldn't make the call in airplane mode, which is not encouraging regarding wifi calling being functional on this phone/provider combo.

[email protected] said:
Thanks for sharing your observations regarding wifi calling. How can one tell it is working? I am used to older phones advising that wifi calling was in use via text in the phone app. I'm not seeing this notification on my new unlocked T-Mobile-branded N20U with Verizon SIM.
I also noticed the VoLTE toggle in the phone app, switched on and greyed-out, can't be deselected. Of course they don't want to support anything but VoIP anymore. What is the behavior, if the cell signal is decent it won't use wifi? It can't be forced to prefer wifi, can it? I used the trick of putting it in airplane mode, then turn on wifi to try and force it to wifi call. It said it couldn't make the call in airplane mode, which is not encouraging regarding wifi calling being functional on this phone/provider combo.
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Click to collapse
From what I've found, if you put another carrier's SIM in a truly unlocked carrier branded phone, it should prompt you to apply your carrier settings upon boot. For example when I put a Spectrum SIM in a Verizon phone, it "converted" the CSC (Carrier settings and boot logo) to Spectrum.
My recommendation is to attempt to get the SIM to switch the CSC automatically. If not, use the patched ODIN to flash the Unlocked U1 firmware, and optionally you can flash Verizon from there if Verizon's Video Calling is a must.

Guyinlaca said:
From what I've found, if you put another carrier's SIM in a truly unlocked carrier branded phone, it should prompt you to apply your carrier settings upon boot. For example when I put a Spectrum SIM in a Verizon phone, it "converted" the CSC (Carrier settings and boot logo) to Spectrum.
My recommendation is to attempt to get the SIM to switch the CSC automatically. If not, use the patched ODIN to flash the Unlocked U1 firmware, and optionally you can flash Verizon from there if Verizon's Video Calling is a must.
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Click to collapse
Thanks for the detailed response. I was a little concerned about the T-Mobile branding, and what that truly meant at the software level. I installed the Verizon SIM to this factory-reset phone. If it was going to switch CSC I think it would have happened then. It went through the usual setup steps, but still displays T-Mobile screen at boot. I'm not sure what else I would do to "get the SIM to switch the CSC automatically".
Would you agree with my conclusion that wifi calling isn't working based on the outgoing call failure when in airplane mode with wifi on?
If there is better, more-unlocked firmware I'm not opposed to flashing it. It's been a while since I've played with rooting and custom ROMS, but I'm guessing stock firmware is a lower-risk activity on an expensive phone.
I'll refer to this link to try and flash to unlocked U1 firmware, hopefully that will allow wifi calling compatibility:
OTA and Non-OTA Firmware for N986U and N986U1

How to enable VoLTE for LG V50 (Korean U+)

How to enable VoLTE on the korean U+? I've checked with my carrier and they confirmed that VoLTE service is active on my SIM. However I can't find any option to enable VoLTE in phone settings. I've only seen a VoLTE call quality option in phone settings - not sure if this means that it's already active. The status bag logo also shows just LTE when mobile data is enabled - no indication of VoLTE.

If you have mobile data showing LTE and it does not change to 3G (or something else) when you make or receive a call, then you are on VoLTE. That is my general understanding of it.

lallolu said:
If you have mobile data showing LTE and it does not change to 3G (or something else) when you make or receive a call, then you are on VoLTE. That is my general understanding of it.
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Yes. It is changing to 3G when I'm making a call.

Sykander said:
Yes. It is changing to 3G when I'm making a call.
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Click to collapse
Ah ok. It seems you are not on VoLTE then. Sorry, I don't know how to activate it though.

i have the sprint version but am currently on tmobile network which (was switching me to 3g) during voice call or txt msg.
now that tmobile has been taking down 3g (and they are working on a tower in my area) i do not even see 3g symbol in notifications anymore. i can complete the call and there is no lte symbol or 3g symbol but call completes but can not use data still.
when i hang up i see lte and can use data (browse the web)
the funny thing is before i went to tmobile i had metro pcs in this area which uses tmobile network and i never had a volte problem so you know this is software and they just want us to buy more phones.
this exact phone worked on metropcs with volte no problem.

Question Force disconnection from mobile network on one SIM

I'd like to force my Pixel 7 to disconnect from any mobile network, without using airplane mode. Do you know a way to achieve this?
Reason for asking this: I will travel abroad and use a secondary SIM to provide me with data, while using my primary SIM with voWiFi (or Backup calling). That'd would keep me reachable on my phone number and allow me to make calls/SMS @home at local rates.
The reason for having my primary SIM disconnected from any mobile network is due to the fact that my primary carrier will charge me for calls/SMS depending on the latest place I got connected to a mobile network. They charge roaming fees even when you're using voWiFi in airplane mode! I have tested this already on a previous trip.
One way would be to select a network manually, or a network that I know it won't connect. However, if I turn on and off airplane mode (to take a flight), the phone will connect to the latest network it connected successfully to.
So my strategy is to connect manually to my home network at home, hoping the phone doesn't magically connect to a network. That's why, I'd like to really make sure that the phone can't connect to any mobile network, just to be sure it won't connect to a network while roaming. But only on the primary SIM. For the other SIM I do want to get connected.
For those wondering, my carrier is T-Mobile NL.

Try messing up the apn details on your sim when abroad. That will prevent connection

The issue is that messing with apn won't prevent the phone to register to a roaming network. That alone will tell my carrier where I am and charge roaming fees accordingly...

@jasalta387 Interesting problem for sure. Can you forward your calls to the secondary (travel) sim and use WhatsApp or Signal to call on wifi? Or leave an auto message giving your foreign number. Any time you connect to the primary network you will be charged, no two ways about it on an Android device. I do believe the iPhone has that capability however. Even if you receive a text on the primary you will trigger a roaming charge. Perhaps the only way to avoid that is turning off the sim entirely while traveling. See if they have an inexpensive international plan?

Indeed, iPhone can easily be disconnected from a cellular network by selecting one that doesn't register. That setting sticks even while cycling through airplane mode or a device reboot. On Pixel this is not the case. Pixel will register again, hence my issue.
I know I could rely on 3rd party apps or services or call forwarding. Problem is that I then need to redirect all people who could reach me to them somehow, while using wifi calling is just fine. Even SMS come and go through it. I just need to not make my carrier aware I'm overseas. Hence my question.
I could use a second device that provides me data and keep my phone all the time in airplane mode. This needs that I carry the two devices all the time with the logistics of charging two phones and all of that. I just want to do it all with my Pixel.
I was thinking one thing: I need to go to the US. Is 3G dead there for good? Because then I could tell my Pixel to use 3G and not allow 2G. That'd keep it away from any accidental network registration upon landing.

jasalta387 said:
Indeed, iPhone can easily be disconnected from a cellular network by selecting one that doesn't register. That setting sticks even while cycling through airplane mode or a device reboot. On Pixel this is not the case. Pixel will register again, hence my issue.
I know I could rely on 3rd party apps or services or call forwarding. Problem is that I then need to redirect all people who could reach me to them somehow, while using wifi calling is just fine. Even SMS come and go through it. I just need to not make my carrier aware I'm overseas. Hence my question.
I could use a second device that provides me data and keep my phone all the time in airplane mode. This needs that I carry the two devices all the time with the logistics of charging two phones and all of that. I just want to do it all with my Pixel.
I was thinking one thing: I need to go to the US. Is 3G dead there for good? Because then I could tell my Pixel to use 3G and not allow 2G. That'd keep it away from any accidental network registration upon landing.
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I'm intrigued by this and would love to find a solution for you. Oh yeah, 3G is dead across the US from all reports. So I'm trying to parse this scenario, let's see if I get this right. You want to have phone calls come into your primary phone line (Sim 1) but no network connectivity for data, right so far. Also you want SMS to the primary while roaming. The problem is that even if you don't get a phone call or text the connection to the network alone will trigger a billing instance, right so far again?
My daughter has an iPhone and turns off data on the sim but can get phone calls and text. As soon as she does though there is a daily billing charge of $10 because she's outside the US. I also think she can connect to wifi and make calls and text without a carrier network. But I'm not sure about. But that aside, how would you like it to work? Would you like it to connect to the network but not get charged unless you get a call or SMS? Because once a call comes in you're roaming charges will ensue. In airplane mode and strictly wifi there should be no charges but you say they bill you anyway right? Are you sure you didn't get a text or something to trigger the charge? I hope I'm reading this right.

My carrier bills calls and SMS based on the country of the latest connected cellular network. So if I don't connect to any network while I'm abroad my carrier will think I never left the country.
I don't want neither data nor calls/SMS on my primary SIM using cellular while abroad. I can get all calls and SMS via WiFi calling on that primary SIM. To get WiFi calling when I'm abroad I will use the data connection on my secondary SIM or any WiFi network.
Because of the need to get the secondary SIM on, airplane mode doesn't help me. So I need my primary SIM to never to any cellular network while I'm abroad.

jasalta387 said:
My carrier bills calls and SMS based on the country of the latest connected cellular network. So if I don't connect to any network while I'm abroad my carrier will think I never left the country.
I don't want neither data nor calls/SMS on my primary SIM using cellular while abroad. I can get all calls and SMS via WiFi calling on that primary SIM. To get WiFi calling when I'm abroad I will use the data connection on my secondary SIM or any WiFi network.
Because of the need to get the secondary SIM on, airplane mode doesn't help me. So I need my primary SIM to never to any cellular network while I'm abroad.
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And if you turn off the sim then even WiFi doesn't work on your primary number?

If the SIM is turned off, then you don't get WiFi calling

Try the 4636 menu
Choose the SIM you want from drop down
3 dot menu top right
Disable data connection

jasalta387 said:
If the SIM is turned off, then you don't get WiFi calling
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Is it possible to adjust the order of airplane mode / network /wifi on-off so as to not allow the sim to connect to the network but still allow wifi on the sim? So for instance, disable the sim, turn on airplane mode, turn on the sim and then enable wifi calling while in airplane mode, turn off airplane mode with data turned off on the sim. I can't believe with no data, calls, sms and only wifi the carrier will charge you roaming. That just doesn't seem right.

bobby janow said:
Is it possible to adjust the order of airplane mode / network /wifi on-off so as to not allow the sim to connect to the network but still allow wifi on the sim? So for instance, disable the sim, turn on airplane mode, turn on the sim and then enable wifi calling while in airplane mode, turn off airplane mode with data turned off on the sim. I can't believe with no data, calls, sms and only wifi the carrier will charge you roaming. That just doesn't seem right.
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@jasalta387
I don't know if you would follow this suggestion...
But in case you are interested in it, this sounds like something you could pull off automatically with something like MacroDroid or Tasker or some other automation app -- even without being rooted! But I concur, it doesn't make sense that a carrier charge roaming when there would be no data, calls, or sms but only wifi....I'm of the opinion (previously stated somewhere in the thread here) that you might've either misread the bill and/or accidentally "caught" a text or transferred a byte of data and it triggered...

Hey there, I know it sounds harsh that a carrier bills this way. It is verified and discussed in a local forum here (in Dutch) https://gathering.tweakers.net/forum/list_message/74880578#74880578
Of course, here there are a few things at play:
1- the carrier wants to have a clear way of communication and support. If you are abroad, those are the prices you pay for. That's it. You know it for sure. They don't want to have to explain how to turn on VoWIFI and explain how to make that working for every phone, or explain to you that you made a call thinking you were on VoWIFI while you weren't. Their approach is crystal clear.
2- the carrier makes some extra income this way. While travelling in the US: for every SMS sent they charge 0.51 EUR, calls placed 1.27 EUR, calls received 0.76 EUR and 2.50 EUR per MB of data. For data, they sell some passes that makes the price more reasonable. Note that unlimited plans for domestic data/calls here start at 25 EUR per month.
3- In The Netherlands (and for pretty much every country in EU) people rely quite a lot on 3rd party apps for calls and texting, especially when you are abroad. WhatsApp is the go-to service, even for domestic communication. People don't even bother using their home carrier when travelling outside of EU. They just remove (or disable) that SIM. So the high cost of roaming is usually left to business users for which companies pay or make better deals with the carriers.
One thing I didn't mention is that in NL, pretty much all carriers limit VoWIFI to Dutch IP addresses. To use VoWIFI you'd need to use a router that tunnels all IP traffic via a VPN that has an exit point in The Netherlands. That's how I conducted my test and verified that all activity using VoWIFI was billed using the same fares as if I was using a roaming cellular network.
I want to try this using a secondary SIM from a Dutch provider, which will give me the Dutch IP address. Backup Calling on my primary SIM will make that SIM to connect to VoWIFI. But to get my home fares, I really need to make sure that my primary SIM doesn't connect to any network while I'm travelling (hence my original request).