[emerongi]

My grandpa accidentally used a phone number to register when he was trying to log in. His original account got promptly locked and for months they would periodically lock it. He had to provide ID proof every time.

I don't use Facebook, but I totally recognize how valuable it is for my grandpa. Sadly, Facebook does not allow any mistakes to be made on its site, which is what older people tend to do when faced with new tech.