Hello! I want to unlock my old iPhone 3G for use with T-Mobile. I currently have... I already installed a jailbroken 4.2.1 on it already and installed cydia. iOS 4.2.1 Modem Baseband 5.15.04 Bootloader 5.09 I've been researching on the possible ways to unlock this iPhone. I really want to downgrade it to 3.1.3 then unlock. But I'm guessing I can't do this because of the baseband. I know about upgrading to 6.15.00 baseband, but I don't want to risk it all, unless there's a way to go back. What are my possible solutions right now? I'm new to this iPhone hacking. I'm more familiar with the Android. Help please?!