When you add UnionPay as a payment method in the App Store, you are required to provide the mobile phone number your card's issuing bank has on file for you.

If you experience issues adding your UnionPay card, try contacting your bank:

1. To add or update your mobile number associated with the UnionPay card.
2. To confirm that the card number is enabled for online purchases.

Some cards do not have mobile numbers associated with them. If this is the case with your card, contact your bank to update or replace it.