Carrier billing lets you pay for apps, games, or subscriptions by charging the...

https://andresssmartcolumns.talesignal.com/posts/how-does-pay-by-phone-work-on-pay-as-you-go

Carrier billing lets you pay for apps, games, or subscriptions by charging the amount 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 purchase is deducted from your available credit