Well AT&T hasn't been good about getting updates back to Samsung, but you can try BB. Also if there is an AT&T Device Center near you, they might update it for you. 611 can tell you I'd there is one close if you don't know. The last option I know of if those don't work, buy a prepaid AT&T SIM, out $5 on it. It will cost you $15 for the SIM unless an AT&T manager decides to give it to you, and then connect to WiFi and check for an update. The SIM card has to be active.
Oh.. If you know someone on AT&T, pop their SIM card in your phone and check for an update.