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

https://magic-wiki.win/index.php/Carrier_Billing_vs_Debit_Card_for_Small_Purchases

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 bill. For pay-as-you-go users, it’s deducted from your available credit