Pay-by-phone transactions make it easy to buy apps, games, or subscriptions...

https://ariassplendidinsight.swiftnestly.com/posts/carrier-billing-vs-bank-transfer-for-digital-purchases

Pay-by-phone transactions make it easy to buy apps, games, or subscriptions without a card. Charges go directly to your monthly phone bill or use prepaid credit, so you can keep track of spending in one place