Apple Card Mastercard is a co-branded credit card. Information about your card is limited and what is shared would be encrypted and Apple would not have the key to decrypt.
The issue is really the subscription. Most credit cards use a service the network offers (Mastercard in case of Apple Card) to use the same number for subscriptions, so they don’t have to be updated. Somehow, your subscription did not get updated like it should have and now the decline.
Easy way to fix this is cancel subscription and then start it again with the new number. You could also contact billing support and they might be able to correct the account number.
I’ve linked several Apple Support articles that will serve as a guide.
If you want to cancel a subscription from Apple - Apple Support
Subscriptions and Billing - Official Apple Support