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

https://bizzmarkblog.com/carrier-billing-for-subscriptions-is-it-easy-to-cancel/

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 amount appears on your next bill. For pay-as-you-go users, the purchase is taken from your available phone credit