Carrier billing lets you buy apps, games, or subscriptions and charge them...

https://riversinspiringblogs.evergrovio.com/posts/is-carrier-billing-good-for-small-online-purchases

Carrier billing lets you buy apps, games, or subscriptions and charge them directly to your phone bill. If you have a monthly plan, the cost appears on your next bill. For pay-as-you-go users, the amount is subtracted from your available credit