Carrier billing lets you pay for apps, games, or services by charging the cost...

https://www.emergbook.win/carrier-billing-lets-you-buy-apps-games-or-services-and-charge-the-cost

Carrier billing lets you pay for apps, games, or services by charging the cost directly to your phone bill. Whether you have a monthly plan or use pay-as-you-go credit, the purchase amount shows up on your next bill or reduces your available balance