( Mobile ) - When you sign up with a GSM provider, you get a phone with a magical SIM card slot. Assuming that you can unlock your phone, all it takes to use your phone with an international provider is to swap out the SIM card. The process is nowhere near as easy with CDMA providers like Telus and Sprint.
Verizon Wireless is promoting worldly travel with the recent announcement of the Motorola Z6cx World Edition Phone. It's basically the the same as the Motorola Z6c which is also available through Verizon, except that the Z6cx has a SIM card slot for when you're traveling abroad. As you can expect, the only GSM bands supported are the non-American ones.
The trade-off for this worldly capability, unfortunately, is that you lose the 2 megapixel camera. So, you've got to ask yourself, what's more important? Taking pictures or seeing the world?