Carrier billing lets you buy apps, games, or digital content and have the cost...

https://magic-wiki.win/index.php/Carrier_Billing_vs_Debit_Card_for_Small_Purchases

Carrier billing lets you buy apps, games, or digital content and have the cost added directly to your monthly phone bill or taken from your pay-as-you-go balance. It's a simple way to pay without entering card details or setting up new accounts