Pay-by-phone lets you buy digital goods by charging purchases directly to your...

https://post-wiki.win/index.php/Carrier_Billing_for_Subscriptions:_What_Happens_If_My_Phone_Plan_Changes%3F

Pay-by-phone lets you buy digital goods by charging purchases directly to your phone bill or prepaid credit. It’s a simple way to pay without needing a credit card, making checkout faster and easier—especially on mobile