Unfortunately most phones with the designation "I" after the model indicates it is an international phone and will most likely lack the 850 Mhz band. However if it has the designation "A" it will most likely lack the 900 Mhz band.
I just got a sony W800i and it does every thing but make phone calls! I was told the 900 GSM band is not in the U.S. so I'm running only on the 1900 band and I live in maine so I need all the towers I can get. Now I need to get a new ''New'' phone!

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic