Hi guys! My friend recently lost her phone and I want to give her my old 3GS for a temporary use. The problem is that the phone is ATT while she is on T-Mobile. So, I was wondering how you get the 3GS that is running on 4.2.1. to unlock? It is jailbroken but I'm not sure with which program, maybe pois0n... something? Any help will be appreciate to format the phone, unlock it, jailbroken, and to the newest version possible. Thanks!