Carrier billing lets you buy apps, games, or services and have the cost added...

https://collinsexpertcolumn.novacrestiq.com/posts/carrier-billing-vs-debit-card-for-small-purchases

Carrier billing lets you buy apps, games, or services and have the cost added to your monthly phone bill or taken from your prepaid balance. It’s a simple way to pay without using a credit card or entering payment details every time