Those of you who purchased an iPhone 4 and are using it on an unofficial carrier were not able to activate FaceTime. There is now a fix for this. It’s called MiTime and from what I read, it’s working well.
MiTime is an app/service for activating FaceTime on phones that are operating on unofficial carriers. It should work worldwide and will use two text messages to activate. You must be able to receive an international SMS message to get activated (see here if you can receive international SMS).
You first have to download MiTime from Cydia for free. Then go to the MiTime site to pay $5.99 for activating the app. Finally, simply follow the easy instructions posted.
This video will show you the whole process (warning: it’s boring).
Please let us know how it works for you.