How to Enable T-Mobile Wifi Calling on AT&T Galaxy S3!

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For those of you who want to run your AT&T Galaxy S3 on T-Mobile, I have good and bad news for you.

First, the bad news is that the AT&T Galaxy S3 does not support T-Mobile 1700Mhz bands for 3G/4G, meaning you will be stuck on edge speeds although voice will work fine.  Also, you do have to unlock the phone first to use it on T-Mobile (I used to unlock SIM).  But for using outside of the U.S. such as Europe and Asia, you should be able to get full 3G/HSPA+ support.

Second, the good news is that you can actually install a T-Mobile Galaxy S3 ROM (such as HighOnAndroid ROM for Tmo GS3), and make use of Wifi-calling if you use a T-Mobile SIM card.  This knowledge could come in handy perhaps for those of you traveling outside the U.S.  You can probably bring your T-Mo sim card with you and put it in your AT&T Galaxy S3 to make/receive free U.S. calls (if you have unlimited plan) using any WiFi network.

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4 Responses

  1. Erie says:

    Is this confirmed? I dont want to take the risk lf bricking my S3. And how can I do this. Unlock the phone, root it, and then install the TMO Rom?

  2. TonyP says:

    Please confirm whether this works – that you can install TMO rom on ATT phone. There’s a big warning on this same page about not doing this:

    but your video is about doing the exact same thing. I really want to enable TMO’s wifi calling on my SGH-i747 and would love to know that this won’t brick my phone.

  3. asif says:

    which rom i should install for SGH-i747 to get wifi calling
    which rom can you reply with link
    your instructions not pointing which rom (T-Mobile Galaxy S3 ROM (such as HighOnAndroid ROM for Tmo GS3), and make use of Wifi-calling if you use a T-Mobile SIM card. )

  4. Al Espinosa says:

    I just unlocked an I717 and 4g LTE is working on Tmobile. I believe Tmobile is operating LTE now that the Iphone is on Tmobile. All of the hardware is the same on the T999 and I747 except for an extra antenna on the lower back plate between the circuit board and the back door. I think the LTE radio has always been there as both T999 and I747 appear on the on both Tmobiles and AT&T S3s main circuit board. If you replace the mid plate or at least the portion that has the antenna you will get LTE on a T999. As a matter of fact the new T999 coming out of Tmobile are labeled LTE.

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