I get a call from a different number every day of the week with a pre recorded message stating that I've won some prize.  The message goes on and on so I usually just hang up.  I've never given anyone this number as the phone belongs to my employer.

Do everyone else a favor and file a complaint with the FCC to get these jerks shut down:
http://esupport.fcc.gov/complaints.htm

They actually do investigate issues like this and shut people down.