Carrier billing lets you buy digital goods or services and charge the cost...

https://www.strobe-bookmarks.win/carrier-billing-lets-you-buy-digital-goods-or-services-and-charge-the-cost

Carrier billing lets you buy digital goods or services and charge the cost directly to your phone bill. Whether you have a monthly plan or pay as you go, purchases either add to your regular bill or are taken from your prepaid credit