I have to update the credit card number for iCloud and cannot delete the one in file. What do I do?

Hi Isastev,

Welcome to the Apple (user-to-user) Community.

Re: "I have to update the credit card number for iCloud

and cannot delete the one in file". 

As Apple requires at least one card on file at all times if you have active subscriptions (like iCloud), you would need to add the new card first.

Re: What do I do?

Check the new card is one that Apple can accept in your country or region:

Payment methods that you can use with your Apple ID – Apple Support

How to: Add a payment method to your Apple ID – Apple Support

How to: Remove a payment method from your Apple ID - Apple Support

or

What to do:

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

If needed:

Billing and Subscriptions:

There is info., available online,

and

a "Get Support" link at the bottom of the webpage (link below)

Subscriptions and Billing - Official Apple Support

All the best :-)