Originally Posted by lomatopo

Of course it works in the U.S.A. (assuming you have a GSM1900-capable phone and have a signal from AT&T or T-Mo) I use it all the time and I never would have suggested it if it wouldn't work.

FWIW, when as a One-2-Call pre-/post-paid customer roaming internationally you are on the AIS/One-2-Call network, you'll see "TH-GSM" on the display of your phone. Every *xxx (messaging) and 900xxx (IVR) service works in the U.S.A., at least they do for me.