If your contract is with Cingular or Tmobile, you should be able to buy one of their prepay phones and use your SIM.
Right now Cingular has the L7 SLVR with iTunes, a 512MB memory card, camera, bluetooth, etc for $89.99. (its not accessible from their front page, but it is available thru here)
http://www.cingular.com/cell-phone-s..._sku=sku430003
The phone can be unlocked using the services on eBay where you just give them your IMEI number and they give you the unlock code. Its pink, but you can also get new housing for cheap from
http://www.cnn.cn. I recently got an L6 SLVR from Cingular for prepaid and have loved it.