Carrier billing lets you pay for things like apps or subscriptions by adding...

https://page-wiki.win/index.php/What_Can_I_Buy_with_Pay_by_Phone_Billing%3F

Carrier billing lets you pay for things like apps or subscriptions by adding the cost to your phone bill. If you have a monthly plan, the charge appears on your next bill. With pay-as-you-go, the amount is taken from your available credit