You can change your payment method in your account settings.

For the App Store:
1. Open Settings -> iTunes & App Store.
2. Tap your Apple ID email and select View Apple ID. You may be asked to log in to your account.
3. Select Manage Payments. If your device uses the Family Sharing function, your payment information can only be changed by the sharing organizer.
4. Modify or remove the information. Tap Remove to delete a payment method.
5. Tap 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).