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

https://highstylife.com/what-does-pay-by-phone-billing-mean/

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