I am trying to add my iPhone 5s to my support profile, to join the list of my other apple products. But after adding my serial number, a message comes up saying that serial number is already listed with a different Apple ID and won't allow me to register it. I bought it second hand and no longer got the persons details. How can I register my iPhone? I have the phone running latest software iOS 8.3.
iPhone 5s, iOS 8.3
iPhone 5s, iOS 8.3