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

https://www.coast-bookmarks.win/carrier-billing-lets-you-buy-things-using-your-mobile-phone-account-instead-of

Carrier billing lets you buy apps, games, or services and charge the cost directly to your phone bill. If you have a monthly plan, the purchase adds to your next bill. With pay-as-you-go, the amount is taken from your available credit