Carrier billing lets you buy digital goods or services and charge them directly...

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

Carrier billing lets you buy digital goods or services and charge them directly to your phone account. Instead of using a credit card, the cost appears on your monthly phone bill or is taken from your prepaid balance