Changing credit card data associated with Apple ID

I tried to change my Wife's Apple ID because our two 4s phones (with different numbers but the same Apple ID) were both ringing when one was called. I tried to make her Apple ID an old AOL account that is still active. When I tried to change her ID to this old account, I get a message that security issues have to be updated (I believe the problem is that my payment accounts data are out of date) It then provides no avenue to update the billing account information to change it -- only ways to change the name, user Id and phone numbers. How can I "clear" this old Apple ID so I can put it on my wife's iphone? Separately, I understand that Apple will no longer accept AOL user names for Apple IDs after March. DO I have to get another e-mail account to solve the original (two phones ringing) problem?