so i got an iphone from a buddy of mine. i put my sim card from my other phone in and get no service. turns out i need a iphone code on my account. so i go to the att store guy puts the code in and hooks me up with a new sim card. so i go home sync up with itunes and nothing comes up in the way of registering of activating. so i just left my sim card in the iphone and while playing an app i get a messgae on the iphone saying "iphone has activated". so a min after that shows up i get full bars and 3g then bam its gone. wifi worked for a few mins then again bam gone. anybody have any idea on what to do? ive tried airplane mode, turning off 3g, restaring the iphone, turning off the iphone and turning it back on. and yes it worked when my buddy had it.