Apple ID will not let me change my credit card, cancel my old on, or add a new one. What can I do?

Thank you for responding. An Apple tech called and explained my situation: As far as I understand, here’s what happened: 5 years ago I disputed a $31 charge on my credit card. At that point, Apple “banned that credit card forever,” though I never knew about it. I have tried several times over the years to switch to that card but always got an error message. I finally investigated it yesterday. Apple’s response: pay the $31 or use a different card. I don’t remember the dispute. I switched to another card and moved on.