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[Q] How do I prevent Samsung Galaxy S 4G from connecting to AT&T?

I have Samsung Galaxy S 4G with T-Mobile in San Francisco.
Whenever I go to an area without T-Mobile signal, the phone connects to AT&T. I called T-Mobile and they said that's because T-Mobile has roaming agreement with AT&T so my phone would connect.
The problem is, when my phone connects to AT&T, I can't make any calls. It says the phone's not registered. T-mobile says that's because I'm in an area that has T-Mobile coverage.
You'd think that the phone would be smart enough to figure out that only emergency calls can be made (which is what BlackBerry does and shows SOS sign). The real problem for me is that, I have WiFi calling enabled with cellular preference, and when I'm in the basement of my office building where there is no T-Mobile signal (but there is WiFi signal), my phone thinks it has cellular signal so it doesn't activate WiFi calling, yet no phone calls are coming in b/c it's not registered to AT&T's cellular network.
Is there a way for me to force my phone to only connect to T-Mobile? I know there isn't on the regular settings menu, but perhaps experts could tell me how to do so using those star-sharp keys listed here (http://forum.xda-developers.com/showthread.php?t=842134)?
Thank you!

Set wifi preferred instead of cellular.
Sent from my SGH-T959V using XDA App

Unfortunately, that doesn't work for me because I move around a lot, and Android WiFi calling feature doesn't have handover.
There's got to be a way to prevent this phone from connecting to AT&T at a low level somehow, no?

How do I do that? Have checked the manual but can't find location where explains how to select wi-fi preferred instead of cellular. Your kind advise will be appreciated

Open WiFi Calling and select settings. You'll see Preference. Select Cellular Preferred.

I think in setting then wireless and network, then mobile networks then network operators click the default settings.... select manual and wait for the carrier to pop up.
Will this solve your problem?
Sent from my SGH-T959V using XDA App

scoop_dtx said:
I think in setting then wireless and network, then mobile networks then network operators click the default settings.... select manual and wait for the carrier to pop up.
Will this solve your problem?
Sent from my SGH-T959V using XDA App
Click to expand...
Click to collapse
yep manual is exactly what OP should do.

if the settings for network operators are set to manual then u select the network u want and it sticks unless u manually select a different network provider. u are in select automatically mode so the phone can switch all on its own. this should solve your problem as other people have already mentioned

I have tried this many times and works as long you don't turn the phone off. After I forced the phone to manually select T-Mobile I checked many times the default setting and it remained in manual until the phone was turned off. When I switched it back on it was again in automatic mode and switching to ATT when signal is low.
Is there a way to prevent this? If not, well , first thing when phone is on in the morning is to check default setting.
5/24 I finally gave up and sold the phone. Samsung says they have not received any claims regarding this issue eventhough you see it frequently in the forums. I returned back to my HTC HD2 and will wait for the G2.

lock your infuse to cdma

Dial *#*#4636#*#* go into phone information scroll down and choose wcdma only and your done default is GSM/WCDMA auto (PRL)

samsungcaptivates said:
Dial *#*#4636#*#* go into phone information scroll down and choose wcdma only and your done default is GSM/WCDMA auto (PRL)
Click to expand...
Click to collapse
please excuse my ignorance, but what would be the purpose of this?

so that it dosent jump around from 3g 2g if its auto and your not using data it automatically defaults to 2g i think to save battery then switches to 3g oir hsdpa 3.5g or what att calls 4g on demand this keeps it locked on wcdma or 4g to my knowledge

samsungcaptivates said:
so that it dosent jump around from 3g 2g if its auto and your not using data it automatically defaults to 2g i think to save battery then switches to 3g oir hsdpa 3.5g or what att calls 4g on demand this keeps it locked on wcdma or 4g to my knowledge
Click to expand...
Click to collapse
seems like it reverts back to auto after a reboot

This makes the phone work on Verizon, right?

MikeyMike01 said:
This makes the phone work on Verizon, right?
Click to expand...
Click to collapse
See that's what I thought too. ATT = GSM, Verizon/Sprint = CDMA.

kwaalude said:
seems like it reverts back to auto after a reboot
Click to expand...
Click to collapse
Mine goes back to auto as soon as I back out of the menu. Am I doing something wrong by using the back button?

wouldn't this, by locking it, render the phone useless when traveling out of area that support that network?

MikeyMike01 said:
This makes the phone work on Verizon, right?
Click to expand...
Click to collapse
roflmao 10char

vbanh said:
Mine goes back to auto as soon as I back out of the menu. Am I doing something wrong by using the back button?
Click to expand...
Click to collapse
Mine does the same thing. did you figure out how to do it? I have been trying but I couldn't do it

I found this here in the forum someone posted and it worked for me thanks for him.
champoux said:
Here's an alternate method I puzzled out (and then afterward discovered it was already posted in thread 751237. It's a bit faster and has the advantage of surviving flight mode; still gets reset upon restart.
Dial *#*#2263#*#* (mnemonic: *#*#BAND#*#*).
This brings up the Band selection menu which you can also access from the above method by dialing *#*#197328640#*#* then going into DEBUG SCREEN > PHONE CONTROL > NETWORK CONTROL.
Select [3] GSM BAND
Select [1] GSM ALL
Select "Select GSM All Bands"
Menu key > END
To switch back, go to *#*#2263#*#* and select [1] AUTOMATIC > Select GSM &WCDMA All Bands > Menu key > END.
Something else I'm trying out is switching the acquisition order so when it is in "dual" mode, it'll try GSM first. Even so, it will still switch to 3g if there's enough signal. Seems to help keep it on 2G though, when it would otherwise cling to a faint 3g signal with 0-1 bars.
To do that, go into the NETWORK CONTROL menu (see above) then
Select [4] AQUISITION ORDER (yes they misspelled it)
Select [2] GSM->UMTS
Select "Select ACQ_ORDER_GSM_FIRST" (at least they abbreviated it correctly)
Menu key > END
This option does not get reset upon phone restart.
Click to expand...
Click to collapse

I did this and now my sms or text messaging don't work help

I had this happen too, but I didn't use the above method. Don't know what happened, but when I checked message settings, I had no number under "Message Center" did a quick google search and found an ATT number "+13123149810"...now it works again.

Did u call the number

Never mind i fixed it.but now in my network type it says umts is that faster then hsdpa and are there any other number sequences i can use to tweak my phone

I'm getting RAT restricted, which I got on my Vibrant but never my Captivate...
How can I change to show the different bands?
Sent from my Samsung Infuse 4G

wcdma and cdma have nothing to do with each other. wcdma is also known as umts, the base part of 3g (and 4g when hspa+). hspa is a protocol that runs on top of this cell technology providing higher data speeds. gprs (known as edge, and some times called gsm) is 2g. you can turn one or another off so the phone does not seek and connect to both services, which could save battery life. even though ive yet to see my phone find less than 3g/4g in houston, i still dont turn it off, just in case.

The Jack of Clubs said:
wcdma and cdma have nothing to do with each other. wcdma is also known as umts, the base part of 3g (and 4g when hspa+). hspa is a protocol that runs on top of this cell technology providing higher data speeds. gprs (known as edge, and some times called gsm) is 2g. you can turn one or another off so the phone does not seek and connect to both services, which could save battery life. even though ive yet to see my phone find less than 3g/4g in houston, i still dont turn it off, just in case.
Click to expand...
Click to collapse
Thanks, John Madden.

How to Fix AT&T Data Throttle Your 4G - Your Data Usage is Among The Top 5% Of Users

How to Fix AT&T Data Throttle Your 4G - Your Data Usage is Among The Top 5% Of Users
There is a nice little APN fix. Just change the APN to Phone and force your phone to use HSPA in your phone's settings. I have instructions with a screenshot...
http://www.traemcneely.com/2011/12/...rottle-4g-data-anti-throttling-trick-for-att/

How do you perform the first step on the skyrocket?
1. Go to Settings > Wireless and Network > Mobile Networks > Click Network Mode and force your phone to use GSM/HSPA (Auto mode).
I don't see "network mode".

Click Access Point Name..
I am now getting 512k vs 150k.
Sent from my SAMSUNG-SGH-I727 using Tapatalk

Found another trick.
I named the access point the same ATT pta, then I put Phone under the APN setting.
Put your phone into GSM/HSPA (auto mode) let it connect to the network,
then go back and put it as HSPA only.....I'm getting 1-2g+ bypassing the throttle using HSPA+ works like a charm.

Att Throttle Samsung Skyrocket
i did all when i click on Mobile networks i see access point names and network operators and use packet data. When i click on network operators is says Default setup doesnt allow me to do anything. Please help

Same here. Don't see 'network.mode' selection. Please help. Does it have to be rooted?
Sent from my SAMSUNG-SGH-I727 using XDA App

I understand there are alot of threds pertaing to this throttling issue. I was given a warning text from att about a week ago now when ever i run my speed test i am only getting around 50kbs thats crazy. I live in pittsburgh which is not an LTE area yet am i screwed? or is there a work around for me????????

there is no network mode on a stock rom.. i posted workarounds on another thread which I started but can't find link now on my phone.. check my profile for my posts
Sent from my SAMSUNG-SGH-I727 using xda premium

*#*#4635#*#*

ajdrausal said:
*#*#4635#*#*
Click to expand...
Click to collapse
*#*#4636#*#*
---------- Post added at 11:36 PM ---------- Previous post was at 11:17 PM ----------
I am still not sure where/how to pick "GSM/HSPA (Auto mode)" on stock rom. Thats not an option.
What I have are:
WCDMA preferred - The GSM phone is capable of using both 2G and 3G data communication and when signal strength is low 3G is favored more.
GSM only - The GSM phone is capable of using only 2G data communication. When the 2G signal is too low you get nothing at all.
WCDMA only - The GSM phone is capable of using only 3G data communication. When the 3G signal is too low you get nothing at all.
GSM auto (PRL) - The GSM phone is capable of using both 2G and 3G data communication and when signal strength is low 2G is favored more. This one is a bit confusing to me since PRL is associated mostly with CDMA technology and not GSM technology.
CDMA auto (PRL) - The CDMA phone is capable of using both 2G and 3G data communication and when signal strength is low 2G is favored more.
CDMA only - The CDMA phone is capable of using only 2G data communication. When the 2G signal is too low you get nothing at all.
EvDo only - The CDMA phone is capable of using only 3G data communication. When the 3G signal is too low you get nothing at all.
GSM/CDMA auto (PRL) - Some phones are equipped with both GSM and CDMA capabilities. This setting appears to just have the phone attempt to stay connected to the data communication type that works the best. (Maybe the Samsung Galaxy S will take advantage of this???)
Unknown - If none of the above fit or the phone is acting weird as far as connecting to the carrier, you will see your preferred network type is set to this
(Cut n paste from another thread, dont know if these are applicable to Skyrocket/LTE)

http://forum.xda-developers.com/showthread.php?t=1342111

Thanks for the pointer to the thread but my whole point is that I dont see those options and for some reason my network mode changes dont stick.
So if I disable packet network, switch the APN, change the network mode and then enable the network again, I see that it has gone back to GSM?WCDMA/LTE auto mode again.
So for some reason my network mode changes dont stick. Also, I am on stock rom, could that be the reason!

activemind said:
Thanks for the pointer to the thread but my whole point is that I dont see those options and for some reason my network mode changes dont stick.
So if I disable packet network, switch the APN, change the network mode and then enable the network again, I see that it has gone back to GSM?WCDMA/LTE auto mode again.
So for some reason my network mode changes dont stick. Also, I am on stock rom, could that be the reason!
Click to expand...
Click to collapse
Custom ROMS give you the options you are looking for.

I am confused ! If the stock radio is *locked* to use LTE if available, why are some people reporting to lock onto HSPA+ network with stock ROM. Are they exploiting some bug?
I have tried various things but I cant switch my radio to anything except GSM/WCDMA/LTE auto mode. It seems to come back to that mode.
Do I need a reboot after changing the mode.
I am using *#*4636#*#* to switch the mode.

Switching APN 's worked like a charm ;o)

TE TOQUE said:
Switching APN 's worked like a charm ;o)
Click to expand...
Click to collapse
Over a year since last post and you decide to necro for no good reason smh.
Sent from my SAMSUNG-SGH-I727 using Tapatalk 2

[Q] Wi-Fi and 3g connection problems

Hi there!
I've some problems with my G-Nexus 5, as wroten in title,
the Wi-Fi and the 3g connection disconnects me during utilizing it,
if i look on the icons of wi-fi or 3g i can see that i'm not receiving any data and i cant continue to surf in web or by enjoying a game online.
So the question is its a hardware or a software problem, and if another one had the same problem.

So noone had this issue?

Sounds like hardware if this happens both to 3G and WIFI.
How do you fix it? Toggle Wifi? Airplane mode? Restart phone?

After a bit it begins to surf something like 5-10 seconds

I get the same problem on my 3G, it doesn't happen while I'm on WiFi. I have to disable/enable data or airplane mode on/off to get this working again. Also I have noticed that when signal changes from 3G to EDGE and then back to 3G I don't have data working. Need to to the same trick to have that back. It's annoying and you don't know when it working or not unless you check your phone....and lose notification from Facebook Messenger or Whatsapp which i use a lot.

I wrote to google lets see what do they say....
I got realy bored about thia issue.

I would verify that your apn settings are correct. Either call your carrier or maybe google your ("carrier name" apn settings). Also... Settings/Wireless & networks/More/Mobile networks/Preferred network type, is correct. I do know that in my case as far as wifi I get better results (quicker to connect) if the "Advanced " settings for "WiFi frequency band" is set to 2.4 GHz only. Default is Auto. Worth a shot.

wantabe said:
I would verify that your apn settings are correct. Either call your carrier or maybe google your ("carrier name" apn settings). Also... Settings/Wireless & networks/More/Mobile networks/Preferred network type, is correct. I do know that in my case as far as wifi I get better results (quicker to connect) if the "Advanced " settings for "WiFi frequency band" is set to 2.4 GHz only. Default is Auto. Worth a shot.
Click to expand...
Click to collapse
Tried does'nt work, i loos the connection anyway

[Q] How to make LTE/GSM default?

some time ago i set the phone to LTE in the testing menu to see what LTE networks it could see. it saw them fine but not for the network i use yet.
the thing is ever since then everytime the phone reboots it seems to default back to LTE only. soi have to ga back in to the test menue and set it back to LTE/ GSM to get the signal back.
Help! why is it still doing this and how can i fix it?

Go to Settings, More... under Data usage, Mobile networks, Preferred network type. Make sure the radio button for 3G is selected.

so i cant leave it on 4g preferred? 4g should be coming to my location in the next coulpe weeks so id not want that to be perminant.
or will setting it to 3g reset things?

ooooooh, did as you said rebooted, 3g locked on. sat back to 4g preferred and rebooted, 3g locked on.
yey! thanks, i dont get why it worked but much appreciated.