You can edit your payment method in your account settings.

For the App Store:
1. Open device settings -> iTunes & App Store.
2. Click on your Apple ID email and select View Apple ID. You may be asked to log into your account.
3. Select Payment Information. If your device is associated with Family sharing, your payment information can only be edited by the sharing organizer.
4. Edit or remove the information. Click None to remove a payment method.
5. Click Done.

IMPORTANT NOTE: Once you’ve changed your payment method, you may see a temporary authorization hold for a small amount on your payment card (iTunes does that to make sure your new payment account is active).