Carrier billing lets you buy apps, games, or services and charge the cost...

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

Carrier billing lets you buy apps, games, or services and charge the cost directly to your phone bill. If you’re on a monthly plan, the purchase will show up in your next bill. For pay-as-you-go users, the amount is taken from your available credit