I posted this in the Carriers>AT&T but thought it better serve here.

I've seen so many threads on putting another SIM card in another phone. Yes, sometimes it will work. DON'T!!! This WILL VOID the manufacturer's warranty. My finance and several others I know have had this happen. Just not with AT&T phones, plans and GoPhones. Verizon, T-Mobile and others too. Please do not swap SIM cards. It'll save you money if your phone has a warranty. Not sure? Call your carrier's tech support. They will be able to tell you.