Payment for iTunes
If my credit card number was stolen and the bank cancelled my card, now I am unable to change my credit card to my new number. How can I fix that?
iPhone 6s Plus, iOS 12
Try via it via https://appleid.apple.com/account/manage
If that also doesn't work contact iTunes Support and see if they can help you do it : http://www.apple.com/support/itunes/ww (click on your country's flag, the country where you live, and which is therefore the country on the account ; click on Contact Support towards the top right ; click on Get Help under 'Talk To Us’)