Somehow Apple has not figured out how to perfect FaceTime over 3G and left it out of iOS 5. However hamzasood apparently has found Apple’s unfinished work and figured out how to natively enable FaceTime over 3G. You need a jailbroken iPhone 4 to do this since the iPad 2 or iPhone 4S hasn’t been jailbroken yet on iOS 5. You can download apps in Cydia like My3G or Facebreak or follow these steps on a jailbroken iPhone 4.
Enable Facetime over 3G in iOS 5 Natively.
1) Download iFile or iExplorer for your pc/mac and launch it.
2) Navigate to : /System/Library/CoreServices/SpringBoard.app/
3) Search for the file named N90Ap.plist and open it
4) Locate the text line that says:
5) Directly below the line shown above, add the following below (no spaces)
6) Save the file before you exit and respring your device.
You should now have a iPhone 4 that can FaceTime anywhere! Well except if you run out of service or are on edge. But just about everywhere.