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[Q] No Service after unlock

I successfully unlocked my Samsung Galaxy S 4G. However when I insert an AT&T sim, I show full bars of signal but the screen says (No Service). I've tried two different sim cards and neither will work. They are both older sim cards but they should still work, right?
Only thing that stands out as odd is the AT&T APN isn't checked blue; it's white (unmarked?) and can't be selected. I'm using Gingerbread 2.3 and my T-Mobile card works fine. I have my network bands set to automatic.
And for the record, in order to connect to AT&T's network, I need to use the AT&T sim all the time, right? I won't be able to connect to AT&T when using the T-Mobile sim, yes?

Tmobile cam connect to AT&T only when data roaming for me if I got to arkansas... Im.at&t. But imma say to try to unlock again
Sent from my SGH-T959V using XDA App

mcbipolar said:
I successfully unlocked my Samsung Galaxy S 4G. However when I insert an AT&T sim, I show full bars of signal but the screen says (No Service). I've tried two different sim cards and neither will work. They are both older sim cards but they should still work, right?
Only thing that stands out as odd is the AT&T APN isn't checked blue; it's white (unmarked?) and can't be selected. I'm using Gingerbread 2.3 and my T-Mobile card works fine. I have my network bands set to automatic.
And for the record, in order to connect to AT&T's network, I need to use the AT&T sim all the time, right? I won't be able to connect to AT&T when using the T-Mobile sim, yes?
Click to expand...
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When you switch Sim cards you have to do a factory data reset. Just enter recovery and select the option to factory reset then reboot it should recognize your new Sim.
Sent from my SGH-T959V using XDA Premium App

I did a factory data reset from Settings->Privacy->Factory Data Reset and it didn't work. Still says No Service.
And I don't think I need to unlock again because when I access that one screen (I forget the code to enter) it shows all the locks as set to OFF.
Any other ideas why the AT&T SIM card won't allow my phone to connect? Is the fact that it's an old card the problem?

mcbipolar said:
I did a factory data reset from Settings->Privacy->Factory Data Reset and it didn't work. Still says No Service.
And I don't think I need to unlock again because when I access that one screen (I forget the code to enter) it shows all the locks as set to OFF.
Any other ideas why the AT&T SIM card won't allow my phone to connect? Is the fact that it's an old card the problem?
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Click to collapse
It could be the sim card although I really dont see how it could be. Is it a 3g sim card? If so it should still work, factory reset, input the at&t apn settings, reboot phone. That is what I would try, I have an unlocked phone as well, and once you input the unlock code, its UNLOCKED.

type in *#06# and let me know what comes up

jdubb1106 said:
type in *#06# and let me know what comes up
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Click to collapse
Didn't think of that, depends how it was unlocked. IMEI could be issue

mcbipolar said:
I successfully unlocked my Samsung Galaxy S 4G. However when I insert an AT&T sim, I show full bars of signal but the screen says (No Service). I've tried two different sim cards and neither will work. They are both older sim cards but they should still work, right?
Only thing that stands out as odd is the AT&T APN isn't checked blue; it's white (unmarked?) and can't be selected. I'm using Gingerbread 2.3 and my T-Mobile card works fine. I have my network bands set to automatic.
And for the record, in order to connect to AT&T's network, I need to use the AT&T sim all the time, right? I won't be able to connect to AT&T when using the T-Mobile sim, yes?
Click to expand...
Click to collapse
you would need to use your att sim card you may have a issue with the fact the sgs4g actually lacks 3g band
its hsdpa or edge or G
unless att uses the same spectrum as tmobile for hsdpa you prob will not get a signal

Thanks for the help everyone. In my newbishness, I didn't understand from the instructions on unlocking that the foreign SIM needed to be active. None of the instructions say it needs to be. That turned out to be the problem: I was using an old, inactive SIM (hence no service).
Sick as I am with T-Mobile, I just took my phone in to AT&T and switched providers yesterday.

AT&T Nexus S work on a foreign simcard without unlock?

Did you have to unlock the phone to do that?
I called AT&T and they said that they don't have the unlock code since they don't even sell the device, but that it works on sims outside the US. She seemed to imply that it won't work on tmobile but that if I go outside the US, and just put a sim in, it will work without me having to unlock the phone in anyway.
Can anyone verify this?
Thanks

dannypp said:
Did you have to unlock the phone to do that?
I called AT&T and they said that they don't have the unlock code since they don't even sell the device, but that it works on sims outside the US. She seemed to imply that it won't work on tmobile but that if I go outside the US, and just put a sim in, it will work without me having to unlock the phone in anyway.
Can anyone verify this?
Thanks
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Click to collapse
Most customer service representatives are pure idiots .... Nexus S is a Google phone , so it's factory unlocked to any SIM card you use with it(you may or may not get 3G on other networks depending on the other network 3G frequencies , and if the forgein network has 3G on 900/1900MHz it will have 3G on this Nexus S)..
Hope this helps..

Well I went to tmobile and the guy put in a sim into the phone and the phone got no reception nor did it seem to recognize the sim at all.
So it seems that it isn't unlocked.
I tried putting in this code: *#7465625#
Its supposed to tell you if the phone is unlocked or not, but nothing happens, it just says: Connection problem or invalid MMI code.
I don't need it to work on tmobile, but I do need it to work on foreign simcards. And I saw on other forums that for some people it worked on tmobile and others it didn't so there doesn't seem to be any clear answers.

dannypp said:
Well I went to tmobile and the guy put in a sim into the phone and the phone got no reception nor did it seem to recognize the sim at all.
So it seems that it isn't unlocked.
I tried putting in this code: *#7465625#
Its supposed to tell you if the phone is unlocked or not, but nothing happens, it just says: Connection problem or invalid MMI code.
I don't need it to work on tmobile, but I do need it to work on foreign simcards. And I saw on other forums that for some people it worked on tmobile and others it didn't so there doesn't seem to be any clear answers.
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Click to collapse
you have another issue here , check your phone

Thanks for the response.
What do you mean by other issue and how should I be checking my phone?
In any case, I put in a simcard that my brother gave me which I believe is from Mozambique on a carrier Vodacom. It asked for the code of the sim when I put the phone is as always, and so I got in putting in 0000.
It then showed no connection to anything whatsoever, also as always.
Keep in mind I did have wifi on.
Then all of a sudden it asked me to update my phone and install something. So I just said yes and it updated and rebooted.
All of a sudden I have bars here and there and it recognizes that tmobile and AT&T are in the area. I also saw I think at the top of the notification bar when I pull down the notifications tab, it said Vodacom. Of course I get no reception whatsoever but that is expected, this sim was a gophone sim in Mozambique.
Does this mean that its unlocked if it is recognizing another sim, even though no confirmation of reception? I plan to try again with tmobile now and perhaps make sure I have wifi connection while doing so and leave it in for longer.
Thanks and please let me know if you have any thoughts.

what ROM you're on now?stock or costum one ? you also might consider a FULL phone wipe.because this might be caused by a difference between at&t apn or other Sim data and the other .check for that

I'm on stock 2.3 that the phone came with. Haven't messed with it at all.
So I assume you saying that if I want to switch to another sim, I should do full phone wipe then? so that the at&t apn doesn't confuse it?
IF it doesn't work with tmobile again, I will try taht, and I will also try to learn what an apn is.
Thanks for the help.

Might work or might not !!! backup all your data and apps first then use the shotgun method lol
But what I am sure of is that Nexus S phones are always unlocked and SIM free..

[Q] Switching from Sprint to AT&T?

Hey Folks,
I have a Nexus 5, which I bought from the Play store and have been using on Sprint for the past year. I'm switching carriers to AT&T and would like to know if my device will work on their network. I went to an AT&T store and tried swapping out my SIM for one of theres but the "AT&T" logo didn't show up on my phone and I wasn't able to use voice/text/data. Then, when I tried swapping my sprint SIM back in I had a ton of trouble, in the end, the sprint store had to factory reset my phone to get it to work again. I guess my question is, are there any specific settings that need to be changed or a specific manner in which i switch the SIM cards to get it to work on AT&T? A Sprint rep told me it work on AT&T but that can't be right, the phone is unlocked after all. Any and all input is welcomed!

A lot of people here use ATT me included. You'll have to change your APN to ATT. You also will have to give them your phones IMEI. After that you'll be all set.

theesotericone said:
A lot of people here use ATT me included. You'll have to change your APN to ATT. You also will have to give them your phones IMEI. After that you'll be all set.
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I used to switch sims between ting(sprint MVNO) and ATT since I work in areas sometimes that does not have att service, and I never had a problem going between the two. Did you try to reset the radio on the phone?

theesotericone said:
A lot of people here use ATT me included. You'll have to change your APN to ATT. You also will have to give them your phones IMEI. After that you'll be all set.
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Click to collapse
chapelfreak said:
I used to switch sims between ting(sprint MVNO) and ATT since I work in areas sometimes that does not have att service, and I never had a problem going between the two. Did you try to reset the radio on the phone?
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Hey guys,
I looked for APN settings on my phone and googled it but I couldn't find those options. I tried updating the profile before, updating the PRL, restarting it multiple times and turning the radio on and off. Also tried switching the network type between Global and LTE options multiple times, which only worked < 1% of the time. Finally, I went to the sprint store where they did a factory reset and now it only works on 3G (no LTE). This is a family plan where we're switching to ATT permanently. My sister is sending me some sort of "customized" SIM card for my phone (they took all of my phones info) that should work on ATT. When I go into ATT again to test out my phone, are there any specific settings I need to change or a certain manner in which I switch the SIM cards to test my phone if it works? I wanna test it with a random ATT sim first and not my "customized" SIM card because our ATT line isn't activated as yet, only sprint is.

[Q] Phone wont stay on LTE

I recently switched from straight talk to verizon's own pre paid plan after being fed up with straight talk. When I first got the service active everything was fine. I flashed the CM11 AOSP rom snapshot. I then proceeded to try and update my roaming capabilities by dialing *228 which the automated system told me was successful and ever since then my phone will not stay on LTE. It will only goto 3G. If i try to force the lte only mode then my data will work but i wont be able to make calls. I have tried going into stock recovery and resetting factory to try and clear the NV and flashing both the kitkat and lollipop RUU to no avail. Any help would be greatly appreciated.

You might have damaged your Sim card by dialing *228, well I don't know about damaged, but I know Verizon phones locked to their network that uses 4G LTE Sim cards are blocked from dialing *228 because of the reasons you described.

rigbyrobot said:
You might have damaged your Sim card by dialing *228, well I don't know about damaged, but I know Verizon phones locked to their network that uses 4G LTE Sim cards are blocked from dialing *228 because of the reasons you described.
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Click to collapse
So maybe i need to go get a new sim card then. Thats what i figured hopefully i can get to the verizon store before work and grab one.

Hey,
Were you able to get it working again?
I have the same issue. I dialed *228 like an idiot and my phone activated on 3G and won't get anything else.
I've had Verizon reset the connection on their side and I went to the store and picked up a new SIM but I still can't get LTE. It's driving me crazy. I've tried restoring to a prior backup, factory resetting the phone. Nothing gets me LTE.

Question Can't seem to get my att phone to work on t-mobile (assurance) work please 😣 help

I just purchased a new galaxy a12 that was pre-installed with att firmware. I had the device network unlocked by att . I have been told from many sources that att phone and tmobile phones are the same type of network and so my active assurance wireless Sim should work fine in the phone I purchased since assurance is on the t-mobile network.. it shows my assurance number in the Sim information and shows assurance in the apn settings but won't connect to data dating the Sims not registered on the network ... how can I get the Sim to connect with the network with this new phone. Would the easiest fix be to just flash with something and if so how can I do that. Thank you for your time!!!

JMoney$hot said:
I just purchased a new galaxy a12 that was pre-installed with att firmware. I had the device network unlocked by att . I have been told from many sources that att phone and tmobile phones are the same type of network and so my active assurance wireless Sim should work fine in the phone I purchased since assurance is on the t-mobile network.. it shows my assurance number in the Sim information and shows assurance in the apn settings but won't connect to data dating the Sims not registered on the network ... how can I get the Sim to connect with the network with this new phone. Would the easiest fix be to just flash with something and if so how can I do that. Thank you for your time!!!
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Click to collapse
Mess around with the settings, I have a phone that was unocked, and it works fine from AT&T to Google Fi (Which is T-Mobile based), so flashing wouldn't equal to the problem being solved, you should go to networks and select it manually.