Carrier billing lets you pay for apps, games, or digital content by adding the...

https://andersonsimpressivecolumn.urbanvellum.com/posts/why-does-my-checkout-ask-me-to-confirm-by-text-message

Carrier billing lets you pay for apps, games, or digital content by adding the cost to your monthly phone bill or subtracting it from your prepaid balance. It’s a simple way to make purchases without needing a credit card or separate payment app