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

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

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