Audiovox SMT 5600 / SPV C500 (HTC Typhoon)

I called a ATT store today and asked them if I could just pay retail without a contract and they said yes. When I showed up the answer was no. I called a different store and they said yes we do it all of the time. I was hoping to get one and unlock it and use on Cingular. Any \one see any problems like internet useage??