Carrier billing lets you buy apps, games, or digital content and charge the...

https://record-wiki.win/index.php/What_Is_the_GSMA_Open_Gateway_for_Carrier_Billing%3F

Carrier billing lets you buy apps, games, or digital content and charge the cost directly to your phone bill. If you have a monthly plan, the purchase adds to your next bill. For pay-as-you-go users, the amount deducts from your available credit