You can edit your payment method in your account settings.

For the App Store:
1. Open device settings -> iTunes & App Store.
2. Tap your Apple ID 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 delete the information. Tap None 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 (this is how iTunes makes sure that your new payment account is active).

For Google Play:
1. Open the Play Store app.
2. Tap the menu icon -> Payment methods.
3. Choose More payment settings. The Google Pay website will open in your browser.
4. Tap Edit under the payment method you wish to modify.
5. Make the changes and tap Update.