Only credit or debit cards and PayPal can be saved.
Blizzard Account Settings
You can add payment methods in your Payment Methods page.
When you save multiple payment methods, the last one saved is automatically set as default. To change your default payment method, click on the Set as Default option next to your preferred payment method.
You can save a payment method while you are buying in the Blizzard Shop.
- Select your product, click Buy Now and select your new payment type and billing address.
- Click Continue to Payment, and enter your payment details.
- Check the box Save this payment method for later and click Pay.
Your payment method will be saved in your Payment Methods page.