According to this site, http://www.apple.com/iphone/LTE/, the same model phone is sold to work on Verizon, AT&T, and T-Mobile LTE. This also looks like the same model that is sold unlocked. I wonder, if you buy it unlocked, if you could use it on Verizon now? It says the unlocked phone needs a GSM SIM, but it is the same model as the Verizon one, right? Or if you bought the Verizon model, you might be able to use it on AT&T LTE now?