i have a $200 Best Buy gift card planning on using it for the new iPhone 7S or 8. i'm with TMobile right now, unfortunately Best Buy does not sell TMobile iPhones. since Verizon iPhones are factory unlocked, can i get a VZ model from Best Buy and use it with my TMobile sim card? I do have an old Verizon sim card at home, but i've read if i insert that card into a Best Buy iPhone, then the phone will be locked to that carrier, so if i do buy a Verizon iPhone from Best Buy (paid in full), do i have to insert the Verizon sim card first to activate it? --- Post Merged, Aug 19, 2017 --- i did a little search around and found out i would have to insert my old Verizon card in first so the phone remains factory unlocked and then put in my TMobile sim card. can anyone confirm this? what if my Verizon sim card is no longer active since i've switched from VZ for a couple years now, would that still work?