Can I exchange my Samsung BlackJack for a new one or another phone?

I have a blackjack from AT&T that I've had since Dec. of 06. It's having trouble making calls indoors. When I first starting using it I had no problems making calls anywhere in my house. Now I have to go outside to even get some decent quality. I had a two year contract which expired Dec. of 08 but I can't remember if I purchased insurance. What can I do about this? Can I exchange this phone for the same model or possibly choose a whole new phone?