Hi, I currently have a AT&T iPhone 4 and 4S, I am going to travel to Taiwan in April and would probably need to unlock both phones so I can use it oversea with the oversea SIM cards. I remember there use to be sticky tutorial thread(s) on this forum but I can't seem to find it anymore. Can someone link me to the thread? Will JB be required to unlock the phone? And are there any downsides unlocking the iPhones? TIA.