Even though they’re unlocked, Verizon iPhones work best on Verizon’s network. A Verizon iPhone 5 will only receive LTE service on Verizon’s network; for instance, if a Verizon iPhone was run on AT&T’s network, it would only receive HSPA+ data, which is significantly slower. So those hoping to get LTE speed at a pay-as-you-go price may be disappointed. Bringing an iPhone over to T-Mobile will result in slower speeds than AT&T. However, if you’re happy with the physical device of the iPhone 5, after your contract is over, you can sign up for a Verizon pay-as-you-go plan and potentially save a lot of money.
AT&T unlocks its devices after their contract is up, and Sprint Nextel said that its iPhone 5s are locked.