like nokia2003 said, if its lock back, not only u can't make call but u also can't receive it. Try go to Setting --> Phone --> show caller id and make sure its turned on.

Hope that helps.

aiyak aiyak ... No kissing kissing here unless ur the opposite sex la. Hahahahahaha. We're here to help ... minus the kissing part. Maxis do have EDGE ... tried it before the company switch to digi. I was charge RM60 just for testing EDGE on this phone. Now no more worries as i'm using the unlimited data plan from digi and the best part is its free. Kekekekekekeke.