You can edit your payment method in your account settings.

iOS|Apple Devices:
  1. Open device settings → iTunes & App Store
  2. Tap 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. Tap None to remove 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).

Google Play|Android devices

  • Open the Play Store.
    1. Tap menu → Account.
    2. Choose Payment methods → More payment settings.
    3. Enter your Google Payments account if asked to do so.
    4. Tap menu in the browser → Payment methods.
    5. Tap Edit under the selected payment method.
    6. Apply the changes and tap Save.