Can I use my iPhone internationally?
The iPhone 4 came in two flavors: CDMA (Verizon, Virgin, etc.) and GSM (AT&amp;T, T-Mobile, etc.).

The GSM phone will work, however it will incur international roaming charges. Your CDMA version on the other hand will not work in most countries outside of the US.

I would recommend upgrading to the 4S or 5 as changing carriers will not change the radio in your phone.