Carrier billing lets you buy digital goods or services and have the cost added...
https://www.slideserve.com/eogernrhbu/is-carrier-billing-the-same-as-paying-by-text-clearing-up-common-confusion
Carrier billing lets you buy digital goods or services and have the cost added to your monthly phone bill or taken from your pay-as-you-go credit. This means no need for credit cards or separate accounts