Motorola RAZR V3

While talking on my RAZR a week ago, it dropped my call and displayed that it had no service. I immediately thought that cingular was having trouble with our local tower, so I just laid it to the side and really didn't think twice about it. An hour later, I still had no service, which was very unusual, so I popped out my sim card and stuck it in another phone I had lying around. Surprise, I had service. I called cingular and it turns out my warranty had ran out a mere 2 days prior so it would cost me $130 and my broken phone to get a replacement. I bought a new antenna and installed it, but still no service. Everything else is fine. It powers on, reads my sim card. Does anyone have any ideas what I could do to fix this?

Thanks!