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

https://charlieeocd131.lucialpiazzale.com/why-do-mobile-operators-put-spending-limits-on-carrier-billing

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 appears on your next statement. For pay-as-you-go users, it’s taken from your available credit