Carrier billing lets you buy apps, games, or services using your mobile phone....

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

Carrier billing lets you buy apps, games, or services using your mobile phone. Instead of entering card details, the cost is added directly to your monthly phone bill or deducted from your prepaid credit. It’s a simple way to pay without sharing bank info