One of the problems with using the iPhone 4 on an unofficial carrier is you lose the ability to FaceTime. Enter MiTime. MiTime is an application available for jailbroken iPhones that activates FaceTime on unlocked iPhone 4s that are running on unofficial/unsupported carriers, such as T-Mobile USA.
The app was first introduced back in August of 2010 and now it has been updated with support for iOS 4.1 and 4.2.1. It works by sending two international SMS messages to activate FaceTime. It is currently the only way to activate FaceTime on unofficial carriers, and in my opinion, it’s definitely worth it.
Follow the guide below to activate FaceTime on your unlocked iPhone 4...