AT&T or T-Mobil

[Brnfox]

I recently gave someone my iPhone 4 which was purchased from At&T but they have T-Mobil how do they make the iPhone 4 work for T-Mobil

 

[Europa]

Moved to iPhone Unlock.

They can use a GEVEY SIM card unlock if it is still on 4.x. There is currently no way to unlock it has been updated to 5.x. Downgrading the firmware to 4.x will not work.