I travel to the US every few months, and I'm tired of paying Orange's extortionate £1.10/min, roundeded to the minute, roaming call charges when I'm over there. My bill goes up by at least £30 after spending a few days over there.

My P800 is about to go out of contract, so I'll be able to get it SIM-unlocked. Will I be able to purchase a pre-pay SIM card in the US with a UK billing address? If not, does anyone know of any UK phone dealers that can supply US pre-paid SIM cards?

Failing any of that, can anyone recommend another UK network that's cheaper to roam in the US?

Thanks in advance.