How to remove a payment method on iPhone

To remove a payment method, go to Settings → Apple ID → Payment & Shipping → tap the card → Remove. If the remove option isn’t available, check for active subscriptions, unpaid balances, Family Sharing organizer status, or device restrictions. Once those are resolved, the payment method can be deleted normally.

Read this article about how to remove a payment method from your Apple Account --> Remove a payment method from your Apple Account - Apple Support

Certain conditions may require you have a payment method on your account:

- You have active subscriptions.

- You are set as the Family Organizer for a Family Sharing plan

- You owe money for past purchases.

- What you want to buy cannot be paid for with account balance.