Apple ID e-mail won't change on iPhone
I wanted to change my Apple ID e-mail address. This change was successfully done and all my apple devices made this change except my iPhone. On my iPhone I still have the wrong Apple ID e-mail address. I want to change this, but every time it asks for the password of the old e-mail address and never accepts it, since this old e-mail address does not belong to an Apple ID anymore. After a lot of trying to create new codes it still doesn't work. The only solution was to reset my iPhone to factory settings. This is not possible because I have to log in to my old Apple ID of which he never accepts the code. In addition, I have already tried to only reset the settings, but this also did not help because it keeps asking to log in again in the non-existent wrong Apple ID.
What should I do?
iPhone 7 Plus