Do we know yet if there are actually different models of the phone? I'd like to reserve for the upgrade program, but there are no 6s Plus available other than Sprint. I use Verizon and occasionally a European sim card. The reason I ask is that my current 6 Plus was purchased as an unlocked "T-Mobile" phone, but turned out to work on Verizon when I switched over. I'm wondering whether I can reserve for Sprint and have it work successfully. Note that under the upgrade program, apple notes the phone will be unlocked. So that certainly isn't an issue; just the radio compatibility.