Carrier billing lets you buy things like apps or digital content and pay using...

https://wiki-coast.win/index.php/Can_I_Use_Carrier_Billing_for_Parking_and_Transit_in_One_Month%3F

Carrier billing lets you buy things like apps or digital content and pay using your phone bill. Instead of entering card details, the cost appears on your monthly bill or is subtracted from your prepaid credit