Carrier billing lets you pay for apps, music, or other digital purchases using...

https://victoriassmartword.publishlane.com/posts/how-do-i-know-if-my-mobile-operator-supports-carrier-billing

Carrier billing lets you pay for apps, music, or other digital purchases using your mobile phone account. Instead of using a credit card, the cost is added to your monthly phone bill or taken from your prepaid balance