Update payment method

Did you follow this article to update your payment info?

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

In the meantime you could also use Apple Gift Cards to pay for your iCloud Storage Plan:

What you can buy with your Apple Gift Card or Apple Account balance - Apple Support

The old card is still listed? You can only remove it after you set up the new payment information.

Did you compare the payment details with Apple and what they can see on their side, if they check your payment info?

Did you check, if your delivery address is correct?