Unlocked Z Flip 5G from T-Mobile stopped working (voice calls do not work) on ATT/Cricket network

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Aug 11, 2022
So back in 2020 I purchased a Z Flip 5G (SM-F707U) from T-Mobile. I paid it off, and then I had it unlocked, and I swtiched over to Cricket (which runs on AT&T network) and did not have any issues for about a year. Then all of a sudden earlier this year (2022), I stopped being able to make any phone calls. Text and data worked fine, but incoming voice calls would go straight to voicemail and outgoing calls would disconnect as soon as I hit the call button. After several frustrating days, and a few calls to tech support, I was advised that AT&T had removed 3G access from their network and that I need to turn on some feature called VoLTE calling or HD calling. Well it turns out that my Z Flip 5G from T-Mobile does not have those features availble, and was basically told that it will never work on the AT&T and Cricket networks and that I needed to get a new phone :(

Now that was the case until today!!! :D

I replaced the SM-F707U TMB firmware with SM-F707U1 XAA firmware (XAA is the firmware that ships if you order unlocked phone direct from Samsung) and now voice calls are working again on the Cricket network. Note that with the old TMB firmware voice calls still worked only on the T-Mobile network. The new XAA firmware has replaced the T-Mobile startup logo with the Samsung logo, and voice calls just work on Cricket without having to change any settings.

Special thanks to the following threads, as I would not have been able to complete this process without them:

This was the key post that helped realize I could use the U1 XAA firmware on my zflip:

How to download patched version of Odin:

Step by step instructions on everything I needed to do:

How to download Frija so you can then download the firmware file you need ... the BL and AP and CP and CSC/HOME_CSC files:

Note that I did NOT need a USERDATA file.
Note that I used the HOME_CSC file not the CSC file.
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