Hi DiasKa,
The following steps address what you're describing specifically, and should provide a solution:
If you can't remove a payment method
If you have subscriptions like iCloud+, have an unpaid balance, or you use purchase sharing, you must keep at least one payment method on file.
* Do you have a subscription? You can cancel iCloud+ and cancel other subscriptions from Apple. When your subscription period is over, remove your payment method.
* If you're in a Family Sharing group and you use purchase sharing, the family organizer must have a payment method on file. If you're the family organizer, turn off purchase sharing, then remove the payment method.
* If you have an unpaid balance, you might not be able to remove a payment method. Instead, change your payment method.
* If you still can't remove a payment method, contact Apple Support.
You can find these steps along with other information that may be helpful, here: Remove a payment method from your Apple ID - Apple Support
If you have followed the steps correctly and you still have the issue, let us know if you get any specific alerts or error messages when trying, as those may help us determine what might be causing the issue.
After you get the old payment method removed, you can follow the steps here to add a new payment method: If you need to change or update your Apple ID payment method - Apple Support
If you still have questions, reach out to Apple Support directly, as this may require closer guidance: Get Support
Cheers!