Unable to update Apple ID payment method

Sign in to your Apple ID account page and edit / update your Apple ID details -> https://appleid.apple.com                                                     

• On the Sidebar click Payment methods -> then tap Payments Methods and tap Manage payment method.

Or see -> Add a payment method to your Apple ID -> Add a payment method to your Apple ID – Apple Support (UK)

• If you want to change your card, you need to add first the new card, then remove the old card.

See also the following Apple articles:

Payment methods you can use with your Apple ID

Payment methods you can use with your Apple ID – Apple Support (UK)

fyi: Not all credit & debit cards seem to work with App Store / iTunes Store, try a different one, or preferably a credit card. If your card is not accepted as a paymenf method, you need to contact your bank.

If you need to change or update your Apple ID payment method

If you need to change or update your Apple ID payment method - Apple Support

If you update your payment method or add funds to your Apple Account balance, It would take about 1 to 3 business days in order to process.

If you're still unable to update your payment method, Contact Apple Support.

You can have a credit- or debit card on file and an Apple Account balance.

Your default payment method will be used first by Apple when you need to make a payment.  

If you have set your Apple Account balance as your default payment method and you have a credit or debit card, you pay from your default payment method.

If you have credit & debit cards, and you have set one card as your default payment method that will be charge by Apple.

If you still need help, get more help and assistant from Apple directly, see Contact Apple for support and service -> Contact Apple for support and service – Apple Support (UK)