Trying to update payment card

Hello Olemom36,

Here are support documents which may have useful information:

Change or remove your payment information from your iTunes Store account (Apple ID) - https://support.apple.com/HT201266

If your payment method is declined, or you have a billing issue with a previous purchase in the iTunes Store - https://support.apple.com/HT203005

If you can't remove your last payment method or use no payment method with your Apple ID - "Learn why you can't use your Apple ID without a payment method in the App Store, iTunes Store, and more." https://support.apple.com/HT203905

#1 in the last link is a frequenct cause, where somebody has a subscription which means you cannot change the payment method. You must wait for the subscriptions to expire, or contact Apple and see if they can resolve the issue.

This is the most direct method:

iTunes [Store] Support - Use this form for assistance with account and billing, code redemption, or purchase questions -->

https://www.apple.com/emea/support/itunes/contact.html

Use this method to get telephone support:

Contact Apple for support and service - "See a list of Apple phone numbers around the world."

https://support.apple.com/HT201232

What happens when you try? Error message(s)? Are you filling in all the requested information?

If necessary, contact iTunes Support. Either use the form or scroll to the bottom of the page in the 2nd link. Follow through the screens to get a chat or telephone option.  You may need to pick a problem that is slightly different than yours to get a chat option.  

iTunes Support

iTunes Support – world wide