Would a US-Purchased iPhone Work Overseas?

[Moneer81]

I live in the US and my dad lives in Paraguay. If I send him a new iPhone 3GS (he doesn't need anything more advanced) then would it work down there?

All the carriers there are GSM.

 

[awadeee]

I live in the US and my dad lives in Paraguay. If I send him a new iPhone 3GS (he doesn't need anything more advanced) then would it work down there?

All the carriers there are GSM.

If the phone is unlocked it will be compatible. Otherwise it would be locked to AT&T and will not work in Paraguay.