Carrier billing lets you buy apps, games, or services and charge them straight...

https://telegra.ph/How-Do-I-Decide-When-to-Use-Carrier-Billing-vs-a-Card-09-08

Carrier billing lets you buy apps, games, or services and charge them straight to your phone bill. Whether you have a monthly plan or use pay-as-you-go credit, the cost is added to your next phone bill or deducted from your available balance