How can I delete my payment method?
I’m trying to delete my payment method but it wouldn’t let me.
Removing a credit card from an account - Change or remove your Apple ID payment information - https://support.apple.com/HT201266 - More information at: https://discussions.apple.com/thread/3251676?answerId=15891166022#15891166022
If you can‘t choose None when you edit your Apple ID payment information - https://support.apple.com/HT203905 - also make sure you don't have any active subscriptions or are set as the Family Organizer for a Family Sharing plan.
You can only choose None when you set your payment method up from the iTunes Store, App Store, iBooks Store, or Mac App Store. None is not an option when you use the Apple ID account page to set your payment method.