DonBacardi makes some good points, but there's one more very important consideration considering we're in North America.
http://www.phonescoop.com/phones/phone.php?p=490 has the specs for the phone. It's GSM, so that only T-Mobile and Cingular are reasonable carriers for the phone.
However, there are two versions of the phone. One is a North American version, which supports the 850, 1800 and 1900 frequency bands; the other is the Eurasian version, which supports 900, 1800, and 1900 frequency bands. If you have the Eurasian version, then only T-Mobile will be useable, as their network runs exclusively on the 1900 band. If you have the NA version, then Cingular is a choice; their network is a hybrid of 850 and 1900 across the US.
--janak