[lukes]

In the UK if the person on the other end hasn't hung up and you dial 999, the call ends. It's the only way I know to force-end the call.

[crististm]

It seems so backwards! Why wouldn't you be able to hang-up if you are the callee? Anyway, it makes it clear now how the scam works.

In a proper telecom setup, if the hang-up time is longer than the flash time (a few hundred milliseconds) then the call should end - period. This allows you to hang up properly while allowing for call waiting features and the like.