You can edit your payment method in your account settings.
- Open device settings → iTunes & App Store
- Tap your Apple ID email and select View Apple ID. YOu may be asked to log into your account.
- Select Payment Information. If your device is associated with Family sharing, your payment information can only be edited by the sharing organizer.
- Edit or remove the information. Tap None to remove a payment method.
- 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).
Google Play|Android devices
Open the Play Store.
- Tap menu → Account.
- Choose Payment methods → More payment settings.
- Enter your Google Payments account if asked to do so.
- Tap menu in the browser → Payment methods.
- Tap Edit under the selected payment method.
- Apply the changes and tap Save.