Carrier billing lets you buy apps, music, or other digital content and have the...

https://milosimpressivejournals.quillnesty.com/posts/carrier-billing-for-subscriptions-is-it-easy-to-cancel

Carrier billing lets you buy apps, music, or other digital content and have the cost added to your monthly phone bill or taken from your pay-as-you-go credit. This method makes payments simple without needing a credit card or separate app store account