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

https://www.bookmark-maker.win/carrier-billing-lets-you-pay-for-digital-purchases-by-charging-them-to-your

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