A video in YouTube has been going around showing an AT&T iPhone 4S was successfully unlocked and the user is now using it with T-Mobile.

The video shows an iPhone 4S running on iOS 5 on baseband 1.00.11 unlocked by doing a few procedures on the iPhone.

The unlock is done by “tricking” the phone that the same AT&T SIM card was used, although a T-Mobile SIM card was already inserted into the phone. It also involves activating the phone multiple times.

This “flaw” may lead to hackers developing an unlock for this latest iPhone from Apple. When this happens, Apple will definitely work on a new patch and release an update – most likely iOS 5.0.1.

The user also claimed that this method will work on iPhone 4 and 3GS. Full written instructions can be found here.

Do you have an iPhone 4S lockted to AT&T? How about a T-Mobile SIM card? How about trying the steps above and share your experience.