I have an ATT Galaxy S3 but I recently switched to TMobile. I don't have the sim card yet, hopefully get it tomorrow, but my ATT sim card has been deactivated. Since I need to unlock my phone to use Tmobile, I was looking at some forums and I could do it using the dialpad and pressing *#197328640# and following some steps. But I read that this was possible in only a 4.1.1 ROM?
Right now I have MIUI v5. Do I have to downgrade in order to use the *#197328640# code and unlock?