Cannot force 3g since Android 12 - Google Pixel 4a Questions & Answers

Phone: Unlocked 4a. Network: Verizon
I have a macro that enabled me to switch between 4g LTE and 3g by toggling the value of the the system setting "preferred_network_mode" between 8 (LTE,CDMA,and EvDo and 4 (CDMA and EvDo). I also would toggle preferred_network_mode1 and 2 as well. Then, switching off and on airplane mode would enable the setting.
After the upgrade to android 12 (or possibly one of the monthly security updates) I can no longer force 3g. The preferred_network_mode value gets updated to 4, but the phone does not change from LTE, even after a restart.
Is there another setting that must be changed in 12 to enact that network change or did they kill that functionality altogether?
And before anyone asks - I know 3g is dying, but I live in AZ and many rural areas have no 4g but still get coverage fine with 3g. I'd like to keep using it until VZW turns it off completely.

PhxCliff said:
Phone: Unlocked 4a. Network: Verizon
I have a macro that enabled me to switch between 4g LTE and 3g by toggling the value of the the system setting "preferred_network_mode" between 8 (LTE,CDMA,and EvDo and 4 (CDMA and EvDo). I also would toggle preferred_network_mode1 and 2 as well. Then, switching off and on airplane mode would enable the setting.
After the upgrade to android 12 (or possibly one of the monthly security updates) I can no longer force 3g. The preferred_network_mode value gets updated to 4, but the phone does not change from LTE, even after a restart.
Is there another setting that must be changed in 12 to enact that network change or did they kill that functionality altogether?
And before anyone asks - I know 3g is dying, but I live in AZ and many rural areas have no 4g but still get coverage fine with 3g. I'd like to keep using it until VZW turns it off completely.
Click to expand...
Click to collapse
Can't you just change that on SIM settings?
There's an option there to choose the preferred connection type. If you choose 3G there, it doesn't work as preferred?
I thought that was that option porpouse.
Cheers!

The SIM settings only allow Global, LTE/CDMA, or LTE/GSM/UMTS.
There is no CMDA/EvDo option.
Manually setting the preferred network mode to 4 should override those options and force CDMA mode, unless the system variable that determines network mode has changed with Android 12.

Related

[2G/3G/3.5G] Preferred Network Types Explained & How To Change It Easily

I'm noticing most of us are on the AT&T Network, yet there are those that do not want or need 3G/3.5G and want to use 2G or have another carrier so they cant take advantage of the speeds because they are on a Network such as T-Mobile.
Obviously someone using primarily or mainly 2G will see significantly more battery life.
This is good for someone that rarely uses data service or goes online using WIFI for the most part.
To change or edit your Preferred Network type go to your Phone app
then enter the following: *#*#4636#*#*
>Phone Information
>Set Preferred Network Type
Now you are able to change and edit the way your phone looks for and uses the Network you are currently on.
The Terms are explained below:
Preferred Network Types change the type of frequency the phone searches for.
Android is used on several devices that can gain access to different cell carriers.
For simplicity, there are two main types of cell carriers, GSM and CDMA.
The following popular data communication technology is associated with each cell carrier type:
GSM = GPRS (2g), EDGE(2g), UMTS(3g), WCDMA(3g), HSDPA(3g) {Cell Carrier examples: AT&T and T-Mobile}
CDMA = CDMA*(2/3g) EV-DO(3g) WiMax(3/4g) {Cell Carrier examples: Verizon and Sprint}
Now that the general stuff is out of the way, here's my take on the Preferred Network types:
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.
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
When using the 'only' options you should still be able to make calls.
To put things into perspective, The Nexus One is set to WCDMA preferred as default and the Droid Incredible is set to CDMA auto (PRL).
My Samsun S does not recognise my sim.The sim works in another phone. I tried to change the preferred networkto CDMA preferred, as it is on "unknown". It does not allow me to change it. Please help, as this new phone is now doorstopper.
Azizj said:
My Samsun S does not recognise my sim.The sim works in another phone. I tried to change the preferred networkto CDMA preferred, as it is on "unknown". It does not allow me to change it. Please help, as this new phone is now doorstopper.
Click to expand...
Click to collapse
Go to your devices section, seriously...
Sent from Team Pirate! Using Tapatalk 2
legend221 said:
I'm noticing most of us are on the AT&T Network, yet there are those that do not want or need 3G/3.5G and want to use 2G or have another carrier so they cant take advantage of the speeds because they are on a Network such as T-Mobile.
Obviously someone using primarily or mainly 2G will see significantly more battery life.
This is good for someone that rarely uses data service or goes online using WIFI for the most part.
To change or edit your Preferred Network type go to your Phone app
then enter the following: *#*#4636#*#*
>Phone Information
>Set Preferred Network Type
Now you are able to change and edit the way your phone looks for and uses the Network you are currently on.
The Terms are explained below:
Preferred Network Types change the type of frequency the phone searches for.
Android is used on several devices that can gain access to different cell carriers.
For simplicity, there are two main types of cell carriers, GSM and CDMA.
The following popular data communication technology is associated with each cell carrier type:
GSM = GPRS (2g), EDGE(2g), UMTS(3g), WCDMA(3g), HSDPA(3g) {Cell Carrier examples: AT&T and T-Mobile}
CDMA = CDMA*(2/3g) EV-DO(3g) WiMax(3/4g) {Cell Carrier examples: Verizon and Sprint}
Now that the general stuff is out of the way, here's my take on the Preferred Network types:
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.
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
When using the 'only' options you should still be able to make calls.
To put things into perspective, The Nexus One is set to WCDMA preferred as default and the Droid Incredible is set to CDMA auto (PRL).
Click to expand...
Click to collapse
This option has not worked on any Sense ROM I have tried for the HTC Inspire. It works great on CM7 but does nothing but stay on 3G on sense.
For sense Rom if you are rooted this is how you do it
From today screen
1. Hit menu
2. Click settings
3. Click wireless and networks
4. Scroll down to mobile networks
5. Choose network mode
6. Change to gsm
This will lock you into edge only. Even after reboot settings will stay phone must be rooted or it does not hold settings
If you want 3g/4g only. Set tab to wcdma only
I am running coredroid 9.4
Sent from my Inspire 4G using xda app-developers app
insanenyc said:
For sense Rom if you are rooted this is how you do it
From today screen
1. Hit menu
2. Click settings
3. Click wireless and networks
4. Scroll down to mobile networks
5. Choose network mode
6. Change to gsm
This will lock you into edge only even after reboot settings will stay phone must be rooted or it does not hold settings
If you want 3g/4g only set tab to wcdma only
I am running coredroid 9.4
Sent from my Inspire 4G using xda app-developers app
Click to expand...
Click to collapse
I have tried this on CoreDroid and ARHD and no luck. Went through settings menu and used the *#*#4636#*#* options and neither one sticks. Could it be my radio and hboot and the interface with Sense?
EDIT: Going to try ARHD again and see. If not, I will try CoreDroid.
EDIT: Still a no go for either ROM...ClearDroid included. So far, I have only been able to do this via either method (plus a built in toggle) via CM7. This begs the question of whether this is a software issue with HTC Sense.
Strange I remember when I was on stock sense Rom the settings wouldn't stick. But as soon as I rooted and downloaded a custom Rom it did stick sorry you are having trouble. Here is my complete rom/radio/kernal
Coredroid 9.4 = Rom
12.56.60.25u_26.10.04.03m=radio
Lordmod 5.0 is the kernal
I also changed my build.prop settings to enable real 4g and tweaked gsm gprs umits huspa hsdpa I do not know if this had any effect on making settings stick
Sent from my Inspire 4G using xda app-developers app
Build.prop tweaks
insanenyc said:
Strange I remember when I was on stock sense Rom the settings wouldn't stick. But as soon as I rooted and downloaded a custom Rom it did stick sorry you are having trouble. Here is my complete rom/radio/kernal
Coredroid 9.4 = Rom
12.56.60.25u_26.10.04.03m=radio
Lordmod 5.0 is the kernal
I also changed my build.prop settings to enable real 4g and tweaked gsm gprs umits huspa hsdpa I do not know if this had any effect on making settings stick
Click to expand...
Click to collapse
Thank you for the feedback. I am running the same radio. I will revisit CoreDroid again. Perhaps editing the build prop is the way to go in this case. It is the one thing I have not tried on any of the ROMs for this phone other than to rename my phone from Desire HD to Inspire (which was only on one or two ROMS). Would you mind sharing your build.prop settings and tweaks so that I can have a baseline to work with? I'll tweak from there as necessary to meet my wants.
I edited only these in build.prop
ro.ril.gprsclass=10
ro.ril.hsdpa.category=28
ro.ril.hsupa.category=7
ro.ril.hsxpa=2
Reboot twice and don't forget to backup your settings
I used prop editor to edit build.prop its easier but I don't have a link for it but I think there is a link in that thread I posted below
All info can be found here
http://forum.xda-developers.com/showthread.php?t=982082
Sent from my Inspire 4G using xda app-developers app
Give build.prop change a try
insanenyc said:
I edited only these in build.prop
ro.ril.gprsclass=10
ro.ril.hsdpa.category=28
ro.ril.hsupa.category=7
ro.ril.hsxpa=2
Reboot twice and don't forget to backup your settings
I used prop editor to edit build.prop its easier but I don't have a link for it but I think there is a link in that thread I posted below
All info can be found here
http://forum.xda-developers.com/showthread.php?t=982082
Sent from my Inspire 4G using xda app-developers app
Click to expand...
Click to collapse
Thanks. I will give this a shot. I have edited the build.prop before but only for the purpose of changing device id name. I don't remember what I used to edit it but I am sure I can find it again. No worries about the backups. I kept copies of original build.prop saved plus did a nandroid right before making the changes. Never can be too careful. Will post results later tonight on whether this was success or not for locking in the ability to switch between bands.
In that thread I posted is the build.prop app 8th or 9th post down. That tweak is just for faster data speeds and I do not think it will lock u on to 2 g or 3g but who knows
Sent from my Inspire 4G using xda app-developers app
insanenyc said:
In that thread I posted is the build.prop app 8th or 9th post down. That tweak is just for faster data speeds and I do not think it will lock u on to 2 g or 3g but who knows
Sent from my Inspire 4G using xda app-developers app
Click to expand...
Click to collapse
No go for 2g/3g options. Have not been able to really say about faster data speeds but definitely something I will keep notes on. Back to where I started. Looks like CM will remain my ROM of choice for now.
Preferred network type set to unknown
Hi frnds.. i had accidently set preferred network type to unknown by going in secret setting by using the code *#*#4636#*#* in my Micromax A54 and now my real imei number is changed into 00000000. My mobile is not recognizing any sim and on notification bar it says ''searching for service''. I am not able to reset previous setting i.e. unknown to gsm auto(prl) or gsm only or wcdma only. Please help me how can i resolve my problem.
Your help will be appreciated. thnx in advance..
hi i have samsung note2 my network show unknow but every thing is ok call sms is fine how to i fix it to my network when i restart it they show gprs but when i call some one they going to unknow
Turns out the device has two SIM card slots - one strictly for GSM, another with WCDMA support. If this is the same for you, change SIMcard slot and the preferred network type will change
legend221 said:
I'm noticing most of us are on the AT&T Network, yet there are those that do not want or need 3G/3.5G and want to use 2G or have another carrier so they cant take advantage of the speeds because they are on a Network such as T-Mobile.
Obviously someone using primarily or mainly 2G will see significantly more battery life.
This is good for someone that rarely uses data service or goes online using WIFI for the most part.
To change or edit your Preferred Network type go to your Phone app
then enter the following: *#*#4636#*#*
>Phone Information
>Set Preferred Network Type
Now you are able to change and edit the way your phone looks for and uses the Network you are currently on.
The Terms are explained below:
Preferred Network Types change the type of frequency the phone searches for.
Android is used on several devices that can gain access to different cell carriers.
For simplicity, there are two main types of cell carriers, GSM and CDMA.
The following popular data communication technology is associated with each cell carrier type:
GSM = GPRS (2g), EDGE(2g), UMTS(3g), WCDMA(3g), HSDPA(3g) {Cell Carrier examples: AT&T and T-Mobile}
CDMA = CDMA*(2/3g) EV-DO(3g) WiMax(3/4g) {Cell Carrier examples: Verizon and Sprint}
Now that the general stuff is out of the way, here's my take on the Preferred Network types:
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.
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
When using the 'only' options you should still be able to make calls.
To put things into perspective, The Nexus One is set to WCDMA preferred as default and the Droid Incredible is set to CDMA auto (PRL).
Click to expand...
Click to collapse
Hi, here's a tutorial on how to change network modes using AT commands: http://www.josemauricio.net/?p=486
When i try to change my network it automatic changes to wcdma preferred.
When i try to change my network it automatic changes to wcdma preferred

[Tweak] FORCE 4G with anycut

This is actually on old hack I used from the G1 forum. This is really useful if you are in an area where 4G or 3G is weak and you phone keeps switching back and forth to edge. Very annoying...
Install AnyCut from market
Open AnyCut and click NEW SHORTCUT
Click ACTIVITY
Scroll down to "Phone Info" and select that.
I renamed the shortcut "FORCE 4G" but you could name it anything.
Click OK
Now open the shortcut on your home screen, and scroll down to the bar that spans across the whole screen. This is the bar that controls all your network types listed here.
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. (FORCE 4G!)
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. (MY FAVORITE ON G2X)
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
Im sure this hack works on all android devices, less options will show for phones w/o that capability.
BetterCut will obviously also work and youll be able to customize an icon for the shortcut
Menu, settings, wireless and networks, mobile networks, network mode, wcdma only.
Won't that do the same thing without all the work?
*#*#4636#*#*
Phone information
Scroll down
Change WCDMA preferred to WCDMA Only
Same thing as well... If youre that desperate for "4g", however, if you lose 4g/3g you lose ALL SERVICE, I believe. I had played with these settings on my n1 last year. In the end, I found WCDMA preferred was the most reliable ;-)
Sent from my T-Mobile G2 using XDA App
DelinQuentisDQ said:
Menu, settings, wireless and networks, mobile networks, network mode, wcdma only.
Won't that do the same thing without all the work?
Click to expand...
Click to collapse
He's talking about changing the hidden menu. There are two menus, if you change it in the non-hidden menu and not on the hidden menu, is different.
This should probably be moved to themes and apps or general. Nothing really developed here, no offense.
jayohwhy said:
He's talking about changing the hidden menu. There are two menus, if you change it in the non-hidden menu and not on the hidden menu, is different.
Click to expand...
Click to collapse
This isn't the hidden menu this is just the phone info menu that you can access with *#*#4636#*#*
Thanks! I skirt the edge of society and there are a few ROMs that I really like to use that don't have this option built-in. Bionix has it but CM7/Faux and others do not have the option available from the mobile networks menu. I'm sure it adds to radio life if you set it to stick with the highest signal since the phone won't be switching towers.
I have a post about this in the Q&A section, but have any of you experience the G2X using only 1X or CDMA data frequencies other than 4g?

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] Setting network mode priority?

I noticed under "Network Mode" that you have four options: LTE, 3G, 1x, Global. Is there any other way to set a priority list (I was able to do this on my S3 with 4.3)? For example, my S3 would have the option "LTE/CDMA/EvDO". If there's LTE use it, if not use 3G or else use 1x. As it works now, when I'm at home I have to manually change it to "3G" so it will connect to my Airave, then "LTE" when I'm on the road.
Is there anyway to prioritize a list of network modes to use so that if LTE is unavailable it will go right to 3G?

[Q] Phone switches carriers down to 2G as preferred instead of up to LTE

Hi all,
Currently using Xperia Z2 with KitKat. My carrier is DST (Brunei). My carrier uses three separate operators - LTE DST, 3G DST, 2G DST, all viewable in the network operators search page.
Quite often my phone decides to drop down to 2G DST operator as the preferred, without desiring to change back up, even with switching on flight mode. If I manually search, I can see all 3 available, and if selecting either 3G or LTE, they operate smoothly for a while - 20mins or until I lock my screen.
I have noticed this with previous phones on this carrier too.
Is there anything that can be done to either lock out the 2G one, or make the phone understand that is only a last resort?
Thanks

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