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

https://bizzmarkblog.com/carrier-billing-for-subscriptions-is-it-easy-to-cancel/

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