Activation lock help?

Hello! Recently when I plugged my iPhone into my computer it said I needed to restore my iPhone to factory settings to be able to use iTunes with it, so I restored it to it's factory settings and now I'm stuck trying to activate my phone. To be exact what it says is: This iPhone is linked to an Apple ID. Enter the Apple ID and password that were used to set up this iPhone. (r.....@yahoo.com), and whenever I put in my Apple ID it says that it cannot be used to activate this iPhone. Apparently this problem happens when you use Find My iPhone and getting the previous owner to remove the device from their account fixes the problem. I'm pretty annoyed because I have never used Find My iPhone and I'm the only person who has ever owned this phone, so I'm not really sure how else to proceed from here. It's an iPhone 6 and it was up to date by the way. Any help is appreciated, thanks.