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How to change CSC for SM-G991U?

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quadrun1

Member
Aug 25, 2010
17
3
Hello,

I have a SIM unlocked S21 from Xfinity Mobile that I'm now using on Verizon Wireless. I need to change the CSC to VZW, anyone know how? I tried all the dialer codes, and also SamKEY but no luck so far.

SamKEY says "unsupported firmware, please downgrade your firmware".
 

quadrun1

Member
Aug 25, 2010
17
3
Thanks, I tried that but somehow it ignores that the VZW SIM card is VZW, and it keeps the CSC as CCT/CCT/CCT.

Even putting in an AT&T sim card, it still keeps it as CCT/CCT/CCT. The carrier name is stuck as "Xfinity Mobile" also, no matter the SIM.

I wish Samsung would implement the "BYOD" thing already for this phone.. Or maybe SamKEY will work eventually...
 

quadrun1

Member
Aug 25, 2010
17
3
What's interesting is that it changes the APN to the correct one automatically for the 3 SIM cards I've tried (VZW, CCT, ATT)

Firmware bug I guess, or Samsung has not yet fully implemented the "BYOD" feature referenced here:

 

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    Since January 2021, it's not easy to change CSC, some people do it by flashing firmwares then block whatever app checks SIM & CSC compatibility.

    You can check this thread if you're into action.