My ex-girlfriend gave me back he iPhone I had under my name for her to use. Unfortunately she left it locked. Any idea on how to unlock the phone so that I can sell it. This is a iPhone 6 running a slightly older version of iOS
Apple added iCloud activation lock with iOS 7. The iPhone 6 came with 8x installed, so there's no option to unlock it, if you don't know the iCloud ID's password to disable Find my iPhone, and remove it from the iCloud ID.
If you are the owner and can prove it Apple will help, I gave my son an iPhone and he couldn't get back in it after an update, I phoned Apple and they had the sale on the their system so I didn't have to produce any paper work.