If your unlocked then you might want to try this from the Dev team blog...
Developer @sbingner (author of TetherMe) has made some excellent progress devising a new hactivation method that kills two birds with one stone for all you ultrasn0w unlockers. *His tool, Subscriber Artificial Module (SAM) tricks your iPhone and iTunes into creating legitimate activation tickets even though youre unlocked with ultrasn0w. *This means you get the full benefit of push applications, and your battery life increases substantially. *If youd like to try it out, check out
Subscriber Artificial Module