As long as the phone is unlocked, then yes you can use it. Just remember, phones that are used in Asia and Europe run on GSM 900/1800/1900. In the US, Cingular primarily uses 850/1900. If you live in the city, you probably would be able to get away with just using GSM 1900. However, if you live in the suburbs, you would have to use a phone that uses 850/1900 because the reception is going to be spotty at best. When looking for an unlocked phone, I'd recommend trying to look for one that is quad band (850/900/1800/1900), so that it can work well on Cingular's network.

So I am kinda fed up with locked phones from all the normal carriers and I want something new and unique. I's a Cingular user, and as far as I can tell all I need to do is buy an unlocked phone that is GSM tri-band enabled and put in my sim card and it'll work. Is this right? Can I buy a phone from a site like ebay hong kong and feel secure that my phone will work (other than the very real possibility that i might get a doa phone and not be able to complain in chinese). Any suggestions? thanks in advance for any help...