I just received a used iPhone 6 through Amazon, advertised as unlocked. I'm in the US but my SIM card is European, so I can't test it right now. Even if I cut it to fit the micro SIM slot, it won't work without the Greek service. The cellular option in settings is grayed (because there is no SIM I'm guessing), so I can't check for an option called mobile/cellular data network. When I go into General--About--Carrier is says Verizon. Does that mean it's locked with Verizon?