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

https://super-wiki.win/index.php/How_Do_I_Explain_Carrier_Billing_to_My_Parents%3F

Carrier billing lets you buy apps, games, or digital content and have the cost added to your monthly phone bill or taken from your pay-as-you-go balance. It’s a simple way to pay without needing a credit card or separate app account