Unable to remove invalid payment method on Apple Account

Check these possibilities:

● If an app or feature on your device is not working, not appearing, or is restricted (grayed out), a frequent reason is it may have been disabled using Screen Time, or by a technology administrator if you are using a device owned by an employer or educational institution.

- Read this support article If your Apple ID or other options are greyed out in Settings —> If your Apple Account is grayed out in Settings, or you can't sign out - Apple Support

Tap your Settings app > Screen Time > Content & Privacy Restrictions > scroll to Allow Changes and turn on.

- If the device is managed (check: Settings > General > VPN (or Profiles) & Device Management), contact the technology department of the organization that is doing the managing.

● Situation where a VPN was preventing action —> Unable to sign out of my Apple ID on my i… - Apple Community

● If a payment method entry is greyed out and you are a Family Sharing member, you cannot add your own payment method unless you are the Organizer or you turn off Purchase Sharing. See How to share apps and purchases with your family - Apple Support

Hello~ Have you tried adding your new payment method first and the deleting the old one?

~Katana-San~