Hello Question_answerplease,
Welcome to Apple Support Communities. You may not be able to remove a payment method if it is linked with a subscription, or have an unpaid balance.
In order to be able to remove this payment method, please follow these steps:
1-See if you have a subscription
To see your subscriptions on your iPhone or iPad, go to Settings, tap your name, then tap Subscriptions. If you have any active subscriptions, including iCloud+, you must have a payment method on file.
If you want to remove all payment methods, you can cancel your iCloud+ plan* and cancel other subscriptions from Apple. When your subscription period is over, try to remove your payment method again.
*Before you cancel your iCloud+ plan, use a Mac or PC to back up your devices.
2-Turn off purchase sharing
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 try to remove the payment method again.
3-Pay an unpaid balance
Learn how to pay an unpaid balance or fix payment method issues.
After the balance is paid, you can remove your payment method.
If you can't remove a payment method from your Apple ID - Apple Support
We hope this information is useful. Kind regards.