calls daily for I.T. refuses to leave message

They just called me asking for my IT director.

I'm a receptionist for a large firm and these idiots keep calling and ask for a Susan Lewis.  We don't have one and we never have.  Then they call back and ask for our IT Manager.  I like to "play" with these yahoos and then tell them off.  That works for about 2 weeks and then another idiot calls with the same thing.

I got a call from this number asking for my first name but a different last name ("Anderson" this time.)  The caller claimed to be from "Nelson Corporation" but had no idea what he was calling about, what Nelson Corporation does, or where he got my number; he only wanted to transfer Mr. Anderson, whoever that is, to his boss.

Repeated calls. Won't leave a message. I can't get them to stop calling.