Pay-by-phone lets you buy digital products or services by charging the cost...

https://delta-wiki.win/index.php/Do_I_Need_to_Type_Card_Numbers_with_Pay_by_Phone%3F

Pay-by-phone lets you buy digital products or services by charging the cost directly to your monthly phone bill or prepaid credit. It’s a simple way to pay without entering card details, making checkout faster and easier on your mobile device