can't change ID
I took over the iphone my wife had as she bought a new iphone. How do I change the apple ID associated with this old phone? I have an apple ID I use with itunes. When I try to edit the email on the phone, my wife's email, the system tells me my email can't be used because it is linked to another apple ID. I guess I need someone to explain the apple ID-email connection
iPhone 7 Plus, iOS 12