Carrier billing lets you buy apps, games, or services and pay for them through...

https://www.thecoastlandtimes.com/sponsored-content/pay-by-phone-how-carrier-billing-quietly-became-an-everyday-payment-method-4a6c068e/

Carrier billing lets you buy apps, games, or services and pay for them through your phone bill. Instead of using a credit card, the charge is added to your monthly bill or taken from your prepaid phone credit