Most U.S. phones use CDMA technology, which does not work abroad. GSM technology is used in most of the world, outside the U.S. You can purchase or rent a GSM phone to use abroad. Purchasing may be more economical if you travel for several weeks or travel repeatedly. You will also need to purchase a SIM card to program GSM phone.
World Phone: a phone that can be used anywhere in the world, depends on cell phone network, frequency, and the phone. Check with your cell phone provider to learn if your phone will work at your destination and if you can install a SIMM for the country you are visiting. Otherwise, the fees are very high. It is usually more economical to purchase or rent a cell phone that can accept a local SIMM. They may be purchased on the internet or when you arrive at your destination.
Calling Card: this is a pre-paid method to place long-distance/international calls. Calling cards can be purchased at any multi-purpose store.
BBM: if you have a Blackberry, this is an easy and free (if you have the unlimited data plan) way to stay in touch with friends and family who also have Blackberry phone devices. Check and make sure that there is no charge for data usage internationally.