Pay-by-phone lets you buy digital goods and services using your mobile device....

https://andresssmartcolumns.talesignal.com/posts/why-telecom-providers-are-involved-in-online-payments

Pay-by-phone lets you buy digital goods and services using your mobile device. Instead of entering card details, charges go directly to your monthly phone bill or prepaid credit. It’s a simple way to pay without sharing sensitive info