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

https://www.thecoastlandtimes.com/sponsored-content/pay-by-phone-how-carrier-billing-quietly-became-an-everyday-payment-method-4a6c068e/

Carrier billing lets you buy apps, games, or services and have the cost added directly to your monthly phone bill or subtracted from your pay-as-you-go credit. It’s a simple way to pay without entering card details or account info