I recently switched to T-Mobile and everything works great but i noticed that when I'm at the mall or malls , I suddenly I get this network busy message when I try to make a call ! And I have signal like 2-4 bars when this happens but yet I can't make calls or use The internet sometimes . I can send text and receive calls but no make calls or surf internet. The location was west Covina if that helps and the other location was near Van nuys . Has anyone else experience this before ? How can i stop this ? I tried Turning of the phone and removing the sim but nothing ! 10 points thanks (: