Carrier billing lets you pay for apps, music, or other digital purchases using...

https://rileysexcellentnews.readspirex.com/posts/is-pay-by-phone-billing-the-same-as-a-mobile-wallet

Carrier billing lets you pay for apps, music, or other digital purchases using your mobile phone account. Instead of using a credit card, the cost is added to your monthly phone bill or taken from your prepaid balance