How do I remove payment method?

1. Open the Settings app.
2. Tap your name.
3. Tap Payment & Shipping. You might be asked to sign in with your Apple ID.
4. From here, you can do these things:

• Remove a payment method — Tap Edit, tap the red Delete button, then tap Remove. If you have an unpaid balance, have subscriptions including an iCloud storage plan, or you use purchase sharing, you can't remove all payment methods. Learn how to remove all payment methods.

See this link for further reference

If you can't remove a payment method from your Apple ID – Apple Support (UK)