Pay-by-phone lets you buy online and charge purchases directly to your phone...
https://holdenssmartblogs.hexaforgey.com/posts/carrier-billing-not-working-what-should-i-check-first
Pay-by-phone lets you buy online and charge purchases directly to your phone bill or prepaid credit. It’s a simple way to pay without needing a credit card, making checkout quicker and easier, especially on mobile devices