What's wrong with my sidekick? PLEASE HELP!!?

I bought a sidekick lx off a guy on craigslist for $50. It's got a few kinks but all-in-all it was a good deal. It's not jailbroken yet but I unlocked it to take my at&t card. My biggest problem seems to be that the phone thinks I'm making a phone call. There's a little phone symbol at the top by the service bars and it won't let me online b/c it says I can't use the network while on the phone.. but I'm not on the phone!! Anybody know what this is and how I can fix it?