GSM Freq Bands

Everything you ever wanted to know about GSM frequency bands:

Two frequency bands are used by GSM services in the US. Two different frequency bands are used by GSM services elsewhere in the world.
Ideally, you’d want a phone that can work on all four bands – commonly called a quad-band phone. But these are still rare and expensive.
If choosing a tri-band phone as a second best choice, be careful which three bands your phone has. Some bands are more useful than others, depending on where you travel.

Dual, Tri, or Quad Band GSM Phone?