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

https://wiki-cafe.win/index.php/How_Do_I_Avoid_Accidental_Purchases_with_Carrier_Billing%3F

Carrier billing lets you buy apps, games, or subscriptions and charge them 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 taken from your available credit