Hi, I'm new to the forum, I just bought this iPhone 3g and it is jailbroken but not unlocked. I am trying to use my T-Mobile sim because the guy said it was "unlocked" but the phone says "invalid sim." I am trying to unlock it so i can use it with T-Mobile so I'm wondering if anyone can help me. I have searched around Google and it seems that some require resets, but I would like input from people who know how to do it properly. I don't want to risk breaking the phone. Basic details: Version 2.2 (5g77) (NOT 2.2.1) Firmware: 02.28.00 Cydia is installed. I'm assuming that it's easy to unlock once it's jailbroken (based on my google research), but I'm new to the iPhone world. Appreciate any help.