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

https://city-wiki.win/index.php/How_Do_I_Pay_With_Carrier_Billing_on_a_Monthly_Plan%3F

Carrier billing lets you buy apps, games, or services and have the cost added directly to your monthly phone bill or taken from your pay-as-you-go credit. It’s a simple way to pay without needing a credit card or separate account