Carrier billing lets you buy digital goods or services and charge them directly...

https://noon-wiki.win/index.php/Carrier_Billing_for_Parking:_What_Happens_If_I_Hit_My_Limit%3F

Carrier billing lets you buy digital goods or services and charge them directly to your phone account. Instead of using a credit card, the cost appears on your monthly phone bill or is taken from your prepaid balance