iphone 4 wont accept username or password to activate

I just purchased a used iPhone 4 from and individual. I live in an area where there is no cell service so I don't care about having the most up to date phone. When I got the phone it was still activated and I did a factory reset after I changed the icloud account and what not to my info. Now when trying to activate the iPhone it comes up enter your apple id and password. When I enter my info in it says this id cant be used to activate. Can someone please tell me what I need to do , Thanks