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

https://wiki-club.win/index.php/Can_I_Use_Carrier_Billing_for_Expensive_Purchases%3F

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