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Thread: Bringing T-Mobile Galaxy S10+ to AT&T?

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    Bringing T-Mobile Galaxy S10+ to AT&T?

    I have a Galaxy S10+, T-Mobile branded, that I bought new directly from Samsung at launch back in March.

    I'm considering moving from T-Mo over to AT&T. I'm willing to buy a month or two of full service to try it out, but I know in general the only real test would also be with an AT&T branded phone (or a modern unlocked high end phone).

    While I would probably buy an AT&T branded phone if I decided to move over, I don't want to invest in that yet. I have unlocked my phone, so that's not a problem.

    Can anyone speak to the compatibility of my T-Mo S10+ on the AT&T network? What would I get, what would I be missing, etc.?

    Best case, maybe it behaves just like an unlocked S10+. But I'm not really expecting that...

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    Well you can google your phone to see if it includes all the LTE bands that att offers. I’m assuming since it’s a newer phone it prolly will have most if not all bands. I think volte might be your biggest issue but someone else can speak to that. Having an iPhone I don’t know directly weather that part will work for you or not.


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    VoLTE/HD Voice and WiFi Calling probably won't work. T-Mobile firmware doesn't support bands 14,29, or 30 but all other bands and CA combos should work.

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    https://piunikaweb.com/2019/03/11/sa...ate-us-models/

    Use this to flash the right firmware if you’re comfortable doing that. You’ll get all of the LTE bands, 256QAM, 5CA, etc. along with Wi-Fi calling and VoLTE.


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    Quote Originally Posted by adam1991 View Post
    I have a Galaxy S10+, T-Mobile branded, that I bought new directly from Samsung at launch back in March.

    I'm considering moving from T-Mo over to AT&T. I'm willing to buy a month or two of full service to try it out, but I know in general the only real test would also be with an AT&T branded phone (or a modern unlocked high end phone).

    While I would probably buy an AT&T branded phone if I decided to move over, I don't want to invest in that yet. I have unlocked my phone, so that's not a problem.

    Can anyone speak to the compatibility of my T-Mo S10+ on the AT&T network? What would I get, what would I be missing, etc.?

    Best case, maybe it behaves just like an unlocked S10+. But I'm not really expecting that...
    It'd be worth trying an at&t SIM to check, first. I can't speak for the S10 +, but after unlocking my at&t Note 9, I can change SIMs between at&t, T-Mo and VZW, getting VoLTE and Wi-Fi calling on all three. It even changed the boot screen and apps to match the carrier; no ROM flash needed.

    Sent from my SM-N960U using HoFo mobile app
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    Quote Originally Posted by jakeuten View Post
    https://piunikaweb.com/2019/03/11/sa...ate-us-models/

    Use this to flash the right firmware if you’re comfortable doing that. You’ll get all of the LTE bands, 256QAM, 5CA, etc. along with Wi-Fi calling and VoLTE.


    Sent from my iPhone using HoFo
    I'll take a look. Thanks!

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    Quote Originally Posted by wannabefree View Post
    It'd be worth trying an at&t SIM to check, first. I can't speak for the S10 +, but after unlocking my at&t Note 9, I can change SIMs between at&t, T-Mo and VZW, getting VoLTE and Wi-Fi calling on all three. It even changed the boot screen and apps to match the carrier; no ROM flash needed.

    Sent from my SM-N960U using HoFo mobile app
    Good call, but no joy. My S10 Plus still turns on as a T-Mobile logo device, and I don't have mobile hotspot (the icon is there in Quick Settings, but it's disabled--and I need that for my work.)

    I did create a new APN based on AT&T's web page for that; the existing APN that the SIM card downloaded was almost the same, but not quite.

    And when I did that, the only change I could see was that the signal strength bars went way up (from 1 bar to 4 out of 5), and the 4G LTE symbol stayed lit. BUT: the speed test tells all. Where I am right this moment, I get 0.30 down and 0.55 up--and that hasn't changed between when I first got the SIM card around noon and when I put in the new APN around 5:30pm. In addition, Network Signal Info Pro shows me at -115dbm on band 4, 811 meters across flat ground from the tower.

    As far as I can tell, the ONLY change the APN made was the signal strength indicator. It now lies and wants me to believe there's tons of signal, where before it didn't.

    I will put the SIM card back in my old Blackberry KEYone, which is factory unlocked and which does offer everything--including hotspot--except wifi calling and VoLTE. I see that between AT&T and Blackberry, they simply decided not to offer that in the unlocked model.

    Swappa prices for Galaxy S9 Plus are decently down, so I may acquire one of those for AT&T to do a true test. Worst case, my Cricket-using wife can use it.

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    Quote Originally Posted by adam1991 View Post
    Good call, but no joy. My S10 Plus still turns on as a T-Mobile logo device, and I don't have mobile hotspot (the icon is there in Quick Settings, but it's disabled--and I need that for my work.) I did create a new APN based on AT&T's web page for that; the existing APN that the SIM card downloaded was almost the same, but not quite. And when I did that, the only change I could see was that the signal strength bars went way up (from 1 bar to 4 out of 5), and the 4G LTE symbol stayed lit. BUT: the speed test tells all. Where I am right this moment, I get 0.30 down and 0.55 up--and that hasn't changed between when I first got the SIM card around noon and when I put in the new APN around 5:30pm. In addition, Network Signal Info Pro shows me at -115dbm on band 4, 811 meters across flat ground from the tower. As far as I can tell, the ONLY change the APN made was the signal strength indicator. It now lies and wants me to believe there's tons of signal, where before it didn't. I will put the SIM card back in my old Blackberry KEYone, which is factory unlocked and which does offer everything--including hotspot--except wifi calling and VoLTE. I see that between AT&T and Blackberry, they simply decided not to offer that in the unlocked model. Swappa prices for Galaxy S9 Plus are decently down, so I may acquire one of those for AT&T to do a true test. Worst case, my Cricket-using wife can use it.
    try this here for the mobile hotspot setup - https://support.t-mobile.com/docs/DOC-39498

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    you misunderstand: everything, including VoLTE and mobile hotspot, works fine when I'm using my T-Mobile S10+ on T-Mobile.

    When I put the AT&T SIM into my T-Mobile S10+, mobile hotspot is disabled.

    And as I said, wannabefree's experience with his older unlocked AT&T Samsung phone does not translate over to my new T-Mobile Samsung phone.

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    Quote Originally Posted by adam1991 View Post
    Good call, but no joy. My S10 Plus still turns on as a T-Mobile logo device, and I don't have mobile hotspot (the icon is there in Quick Settings, but it's disabled--and I need that for my work.)

    I did create a new APN based on AT&T's web page for that; the existing APN that the SIM card downloaded was almost the same, but not quite.

    And when I did that, the only change I could see was that the signal strength bars went way up (from 1 bar to 4 out of 5), and the 4G LTE symbol stayed lit. BUT: the speed test tells all. Where I am right this moment, I get 0.30 down and 0.55 up--and that hasn't changed between when I first got the SIM card around noon and when I put in the new APN around 5:30pm. In addition, Network Signal Info Pro shows me at -115dbm on band 4, 811 meters across flat ground from the tower.

    As far as I can tell, the ONLY change the APN made was the signal strength indicator. It now lies and wants me to believe there's tons of signal, where before it didn't.

    I will put the SIM card back in my old Blackberry KEYone, which is factory unlocked and which does offer everything--including hotspot--except wifi calling and VoLTE. I see that between AT&T and Blackberry, they simply decided not to offer that in the unlocked model.

    Swappa prices for Galaxy S9 Plus are decently down, so I may acquire one of those for AT&T to do a true test. Worst case, my Cricket-using wife can use it.
    It sounds like VZW and T-Mo will accept the ATT ROM user data, but not the other way around.

    I noticed that the signal bars were more "honest" with the att Oreo ROM; it seems more bars is part of the "5Ge" marketing efforts.

    It's odd that you had such terrible UL/DL speeds with the correct APN.

    Good luck with your efforts. I look forward to hearing your resolution.

    Sent from my SM-N960U using HoFo mobile app

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    You definitely need the att rom to get all the network has to offer. Right now, you're running a tmo modem on at&t's network. Not a good mix.

    Sent from my SM-N960U 6GB aka Note 9 using Tapatalk

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    Quote Originally Posted by 10mm View Post
    VoLTE/HD Voice and WiFi Calling probably won't work. T-Mobile firmware doesn't support bands 14,29, or 30 but all other bands and CA combos should work.
    The Phone will automatically download Att's firmware with the sim card so all bands will work.

    Sent from my SM-G965U1 using Tapatalk

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    Quote Originally Posted by thotguy31 View Post
    The Phone will automatically download Att's firmware with the sim card so all bands will work.

    Sent from my SM-G965U1 using Tapatalk
    apparently not. But remember, this came from Samsung as a T-Mobile branded phone.

    The AT&T SIM card did nothing to make it not be a T-Mobile branded phone, it appears.

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    Quote Originally Posted by thotguy31 View Post
    The Phone will automatically download Att's firmware with the sim card so all bands will work.

    Sent from my SM-G965U1 using Tapatalk
    BYOD firmware for the S10 isn’t out yet. Typically this feature gets added around December from past Galaxy phones (S8, S9).

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    Quote Originally Posted by thotguy31 View Post
    The Phone will automatically download Att's firmware with the sim card so all bands will work.

    Sent from my SM-G965U1 using Tapatalk
    Nope. If you insert an AT&T SIM in an S10 running T-Mobile firmware you won't have bands 14,29, and 30 as it doesn't require a restart (firmware change)when changing SIMs. Same with my AT&T branded S10, I can insert a VZ SIM but it lacks B13 and service menus stay enabled.

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