I have voicemail on a number of lines, it is simply saying nobody is available to take the call, and then a beep.
However, we have started getting a new type of junk calls for debt management. Like many illegal pre-recording message calls they ask you to press a key to talk to them. That way they do not tie up operators with hang-ups and voicemails and so on. The key they ask you to press this time is 5.
So I changed the "beep" at the end of the message to be a DTMF 5. It's a beep, why not :-)
It worked. Not tying up much time, but better than nothing. I may have to see if I can light up a million numbers or so for a while to work like this just for fun.
MP3 Recording - best so far - well over a minute wasted
Update: The tar-pit is primed - I'll see if I get some nice calls to post indue course.