Question

Will unlocked phones work with T-Mobile Wifi calling ?

M
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If I purchase an unlocked phone, for example an S22 Ultra unlocked version, will I be able to make Wifi calls on T-Mobile ? This is assuming I use a T-Mobile SIM with it, or eSIM, of course.

The reason I ask is that I have no reliable cell coverage at home. Neither 3G/4G/5G offer reliable signals in all places in my home from any operator. A T-mobile cellspot in-home LTE tower also does not cover my entire home. The only thing that works reliably is Wifi calls, using a combination of 5 wireless access points.

My current phone is a T-mobile version (Note 20 Ultra) and works with Wifi calls. I need my next phone to continue to work with Wifi calls. Some unlocked phones are available for significantly less than the T-mobile versions, for example the S22 Ultra version sold by Google on Fi is $700 vs $1200 on t-mobile.com . But will it work with T-mobile Wifi calling ?

 

12 replies

syaoran
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Userlevel 7
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Samsung U1 models are compatible with T-Mobile's WiFi Calling implementation.

Syaoran - I am not a T-Mobile Employee but I could use a new job!
M
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Samsung U1 models are compatible with T-Mobile's WiFi Calling implementation.

How would I know which model is a U or U1 and who sells it ?

FYI, my current Galaxy Note 20 Ultra is a SM-N986U, not U1, and supports T-Mobile Wifi calling. It was bought from T-Mobile and unlocked my T-Mobile, though. It wasn’t unlocked from the start.

 

syaoran
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Userlevel 7
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The T-Mobile U will.obviously support T-Mobile's WiFi Calling.  The U1 is the non-carrier model that is sold unlocked directly from Samsung.  

Syaoran - I am not a T-Mobile Employee but I could use a new job!
M
Badge +1

The T-Mobile U will.obviously support T-Mobile's WiFi Calling.  The U1 is the non-carrier model that is sold unlocked directly from Samsung.  

Thank you. I guess that means the S22 Ultra sold by Google would be the U version and wouldn’t work, then. Sigh.

syaoran
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Userlevel 7
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The T-Mobile U will.obviously support T-Mobile's WiFi Calling.  The U1 is the non-carrier model that is sold unlocked directly from Samsung.  

Thank you. I guess that means the S22 Ultra sold by Google would be the U version and wouldn’t work, then. Sigh.

Google Fi uses the T-Mobile network primarily.  If you feel comfortable doing it ing so and if the device is SIM unlocked.  The U's can be converted to U1 models via a firmware cross-flash.  XDA Developers is your best place to figure out if you are comfortable with that.  

Syaoran - I am not a T-Mobile Employee but I could use a new job!
M
Badge +1

The T-Mobile U will.obviously support T-Mobile's WiFi Calling.  The U1 is the non-carrier model that is sold unlocked directly from Samsung.  

Thank you. I guess that means the S22 Ultra sold by Google would be the U version and wouldn’t work, then. Sigh.

Google Fi uses the T-Mobile network primarily.  If you feel comfortable doing it ing so and if the device is SIM unlocked.  The U's can be converted to U1 models via a firmware cross-flash.  XDA Developers is your best place to figure out if you are comfortable with that.  

Thanks. I’ll take that into consideration. Seems a bit of pain to have to do that. I wonder why the T-mobile Wifi calling would work on some versions of the phone and not others. Is there a technical reason ? You need a T-Mobile SIM/eSIM in all cases anyway.

syaoran
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Userlevel 7
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It's the firmware that makes the different.  AT&T  Verizon, and other carriers choose to use custom implementations of WiFi Calling that are set in their firmware versions.  It is controlled at the carrier profile level, meaning you just can't switch it in most cases.  

Syaoran - I am not a T-Mobile Employee but I could use a new job!
A

If you have a device with model ending in U1U factory unlocked from Samsung or these newer models ending in U1 you can flash whatever carrier firmware you want on to the device (granted it's a U.S. carrier) and use it. You have to know what you're doing though as to not brick your device. It's not hard but one wrong move and you could end up with a bricked device which is fixable it just has to be flashed correctly. The wifi calling you're looking for would be on said firmware. Wifi calling isn't a hardware function so flashing would give you the wifi calling you want.

T

The reason I ask is that I have no reliable cell coverage at home. Neither 3G/4G/5G offer reliable signals in all places in my home from any operator. A T-mobile cellspot in-home LTE tower also does not cover my entire home. The only thing that works reliably is Wifi calls, using a combination of 5 wireless access points.

Is a cellspot the same thing as a cell signal repeater?  I get 4G at my house but it is really spotty, and wifi calling seems to be just as spotty for me.  I’ve been thinking of getting a repeater but they cost as much as a mid to premium tier smartphone, depending. 

 

Also, I was thinking of getting a Note 20 Ultra just for the SD card slot, but a new one costs almost as much as my primary choice the Xperia 1 III (which doesn’t even seem to fully work with tmobile). 

 

F
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Userlevel 7
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The reason I ask is that I have no reliable cell coverage at home. Neither 3G/4G/5G offer reliable signals in all places in my home from any operator. A T-mobile cellspot in-home LTE tower also does not cover my entire home. The only thing that works reliably is Wifi calls, using a combination of 5 wireless access points.

Is a cellspot the same thing as a cell signal repeater?  I get 4G at my house but it is really spotty, and wifi calling seems to be just as spotty for me.  I’ve been thinking of getting a repeater but they cost as much as a mid to premium tier smartphone, depending. 

 

Also, I was thinking of getting a Note 20 Ultra just for the SD card slot, but a new one costs almost as much as my primary choice the Xperia 1 III (which doesn’t even seem to fully work with tmobile). 

 

rumor is Verizon private labeled the Xperia 1 III for themselves..nothing so far fully confirming this though.

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T

Hmm...that would kind of make sense, but that would be too bad for me.  I just switched to Tmobile earlier last year, too.  Thanks for your input. 

L

FYI- I ordered a renewed unlocked version N20U direct from Samsung today for $700. Reg. $850 but they have $150 instant savings. Plus if you use Rakuten, you can get 3% back.

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