How to Unlock iPhone 4s, 4 & 3GS without Jailbreak????

Description:
Well, here's a new trick has been discovered by developer called Michael Capozzi, this trick allows users to unlock iPhone 4S, iPhone 4, iPhone 3GS without jailbreak and without Gevey SIM.
He has been kind enough to also give the following step-by-step guide to unlock iPhone 4S using the bug in iOS 5 to work on T-Mobile USA:
Note: You will need to cut the T-Mobile SIM to micro-SIM size for it to fit iPhone 4S's SIM tray.
Note: Only AT&T iPhones can be unlocked with this trick.

Instruction::
Step 1: Insert original carrier AT&T SIM card