Carrier billing lets you pay for apps, games, and other digital purchases by...

https://dibz.me/blog/why-do-carriers-cap-carrier-billing-daily-or-monthly-1245

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