i purchased a brand new Iphone 6 S plus and used for a few days, now a different apple ID is linked to it, a Yahoo account that i never had.
I gave away to my wife and went through all steps do deactivate and erase the phone. After the process was done i went to reactivate with her apple Id, and now different apple id is linked. I never had a yahoo account. Sent apple the invoice , as the phone was purchased in a apple store. has been a week and so far no news.
iPhone 6 Plus, Activation Problems