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

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

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 credit. This way, you don’t need a credit card or separate account