Roam like a local by changing SIM cards.
Avoid roaming charges and higher rates by using an international SIM
card in your unlocked GSM tri- or quad-band phone or device. Buy a card
online at sites like cellularabroad.com (from $39 with up to 100 minutes). Cards include starter minutes that
can be topped up. Be sure your phone has the right GSM frequency for
your destination (e.g., 900–1,800 MHz for Europe and most of Asia).
Pros: Per-minute rates are usually less than a dollar; incoming calls are often free.
Cons: You can’t keep your regular mobile number—you get a temporary international one with your SIM card.