Last night when I first set up my 6s, I was greeted by a screen say "device activated on CDMA. To roam you need a sim.." I don't remember the exact message but the content was something like that. It appeared after the first few options (choose nations..etc). I was pretty sure the phone was under my device support profile and it was T-Mobile GSM. Anyone has any idea? Note that I bought 2 and the first one didn't show me this message.