Carrier billing lets you pay for digital purchases by adding the cost to your...

https://web-wiki.win/index.php/Why_Does_Carrier_Billing_Feel_Faster_Than_Card_Checkout%3F

Carrier billing lets you pay for digital purchases by adding the cost to your monthly phone bill or by using the credit you have on a pay-as-you-go plan. This method is easy to use since you don’t need a credit card or separate app