They have called me a few times without leaving a message.  I dialed the number, and a recording says, "thanks for calling, the survey you were called for has now finished...."  But, they don't identify themselves as what company name, and survey about what.  If they don't say what kind of survey and who is conducting it, I'm not going to talk to them.  To me, if they don't identify themselves and openly state what kind of survey they're calling for, they're hiding something.  My momma taught me not to talk to strangers. :)