Emulate a recording and say --

"The number you have called is listed on the national no-call list. You have just cost your employer ten thousand dollars. Will you please repeat your name, and the name of the company for whom you are calling. This call is being recorded."

Most likely, the next thing you hear will be a "click."

Unfortunately, when you list your number on the no-call list, there is still a 90 day "grace period" before the bastards are required to stop calling, but it is fairly easy to file a complaint once you're on it.

John