That's a great question cy1031. 4G devices all come unlocked for use with other carrier SIM cards outside of the US. If you're traveling back home for a short period of time, check out our global roaming rates at vzw.com/international.
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You cannot use it on another carrier in the US but you can outside of the US. The SIM card is in a slot on the top of the phone. Nokia made it very very easy to swap SIM cards. This truly is an easy to use international phone.