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

https://telegra.ph/How-Does-Pay-by-Phone-Work-on-Pay-As-You-Go-09-08

Carrier billing lets you buy apps, games, or digital content and charge the cost directly to your phone bill. If you’re on a monthly plan, the purchase appears on your next bill. For pay-as-you-go users, the amount is deducted from your available credit