I've let this caller go to the answering machine before and they never leave a message. Today, I answered the phone before checking my list and there was a real person on the line, but she did not identify herself, just asked for the boss. When I said he was out and asked if he could call her back she just said "When can I call him back?" You know, if she was someone we do business with, then she'd leave a callback number or  a message. I'm updating my caller id to tell us not to answer calls from this number.