[Q] T-Mobile branded S3 somehow became AT&T.

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Apr 23, 2014
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When I received my S3, it was on a T-Mobile branded stock firmware 4.1.1. I wanted to try CyanogenMod, so I installed it, but didn't like it.
Here's where my problem begins. Upon wiping my phone back to stock to get rid of CyanogenMod, I find that it's now AT&T branded, despite the physical phone being a T-Mobile T999.
I tried rooting it and using CSC changers, but those tell me that the PreconfigUI is SingleCSC, and thus apparently unchangeable.
What I want to do is somehow get my phone back to T-Mobile branded stock.

P.S. I do not have a MicroSIM yet.
 

Larry2999

Senior Member
Feb 7, 2014
363
78
Atlanta, GA
When I received my S3, it was on a T-Mobile branded stock firmware 4.1.1. I wanted to try CyanogenMod, so I installed it, but didn't like it.
Here's where my problem begins. Upon wiping my phone back to stock to get rid of CyanogenMod, I find that it's now AT&T branded, despite the physical phone being a T-Mobile T999.
I tried rooting it and using CSC changers, but those tell me that the PreconfigUI is SingleCSC, and thus apparently unchangeable.
What I want to do is somehow get my phone back to T-Mobile branded stock.

P.S. I do not have a MicroSIM yet.

Can you go to your phone's settings => about device and check what the firmware settings are? Let's see what you have under firmware version, baseband version & build number. If possible, you may post a screen shot. Did you say you returned to stock by wiping your phone? Hardly seems likely and you would have probably needed to flash some firmware. Would you recall what you flashed?
 
Apr 23, 2014
6
0
Thanks for stepping up. My phone's info is:

Android Version is 4.1.1
Baseband is I747UCDLK3
Build is JRO03L.I747UCDLK3

I did not flash any firmware, as I had no reason to.
 

Larry2999

Senior Member
Feb 7, 2014
363
78
Atlanta, GA
Thanks for stepping up. My phone's info is:

Android Version is 4.1.1
Baseband is I747UCDLK3
Build is JRO03L.I747UCDLK3

I did not flash any firmware, as I had no reason to.

It's definitely on AT&T firmware. Apologies if I sound like I'm doubting you but are you certain it had T-Mobile firmware when you acquired it? I'd guess it was probably already an AT&T phone. If you bought it in the secondary market, there could have been some previous repairs involving parts swaps. Your safest bet may be to leave it as is and unlock for you use on T-Mobile. Trying to force on T-Mobile firmware now could result in a brick. As it is on 4.1.1, you can easily free unlock it by following the well tested method you'll find elsewhere in this forum.
 
Apr 23, 2014
6
0
No apologies needed. I forgot to state that the phone was purchased with the T-Mobile boot animation and bloatware already present, and that the model number printed below the battery is T999. I've got no clue if there was a parts swap or not. Is the method to unlock that's posted elsewhere that you're referring to the one that begins with you dialing *#197328640#? If so, i've tried it but never got the unlock message to show.
 

Larry2999

Senior Member
Feb 7, 2014
363
78
Atlanta, GA
No apologies needed. I forgot to state that the phone was purchased with the T-Mobile boot animation and bloatware already present, and that the model number printed below the battery is T999. I've got no clue if there was a parts swap or not. Is the method to unlock that's posted elsewhere that you're referring to the one that begins with you dialing *#197328640#? If so, i've tried it but never got the unlock message to show.

There could have been a previous JTag operation involving forced firmware installation on the MB. I've seen previous hybrid firmware involving one or other partition belonging to a different model - e.g. the modem, bootloader or something else but not the complete system.

Yes, that's the unlock method I was referring to. You won't get any confirmation that the process worked at the end. However, if you did it correctly, you would know it worked when you insert a non-compatible SIM card and it works. You should also be able to install T-Mobile apps especially the Wi-Fi calling app which is a really nice feature of T-Mobile.
 
Apr 23, 2014
6
0
I'm getting it microSIM'ed tomorrow. I'll see how that goes.

UPDATE: Successfully obtained and installed T-Mobile microSIM. Still wish to replace AT&T boot animation and bloatware with T-Mobile's, though.
 
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Larry2999

Senior Member
Feb 7, 2014
363
78
Atlanta, GA
I'm getting it microSIM'ed tomorrow. I'll see how that goes.

OK. I'd be interested in knowing the outcome but I'll be surprised if it isn't unlocked already. Did some further research and there have been some reports of people successfully 'flashing' AT&T firmware on T-Mobile phones, and vice versa. Not sure why this should happen and conventional logic suggests the result should be a hard brick which is indeed the most common outcome. I'll also suggest you boot into download mode and see the information under bootloader. If the device has a T-Mobile bootloader, it may be possible to remove the OS via custom recovery and re-flash T-Mobile firmware.
 
Apr 23, 2014
6
0
Download mode currently gives Product Name as SGH-I747. Wiping AT&T OS via custom recovery and then installing the proper one sounds like a good lead. I eagerly await your instruction :)
 

Larry2999

Senior Member
Feb 7, 2014
363
78
Atlanta, GA
Download mode currently gives Product Name as SGH-I747. Wiping AT&T OS via custom recovery and then installing the proper one sounds like a good lead. I eagerly await your instruction :)

If download mode info shows secure bootloader enabled, the phone is, to all intents and purposes, now an AT&T phone. Attempting to flash T-Mobile firmware may likely result in a brick which would require a JTag fix. I was hoping download mode would show it still had a T-Mobile bootloader which could have allowed for safe firmware installation but this does not appear to be the case. Likely the motherboard was previously replaced or it suffered a brick and AT&T firmware was JTagged on. Either way, it would be safer to leave it as is.
 
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