Carrier billing lets you buy digital goods or services and charge the cost...

https://www.bookmarkmaster.win/carrier-billing-lets-you-buy-apps-games-or-other-digital-content-and-charge

Carrier billing lets you buy digital goods or services and charge the cost directly to your phone bill. If you have a monthly plan, the purchase shows up on your next bill. With pay-as-you-go, the amount is taken from your available credit balance