Calling to offer "free consultation". I told them I'm on the National Do Not Call List and she said "that doesn't apply because we aren't selling anything". I told her it's also illegal for her to call if I haven't either contacted their business in the last 3 months asking for a phone call or done business with them in the last 18 months. She hung up.

This is a Caller ID Spoof number. It's a fake number created by computer software to fool your caller id system. The guy on the other line was trying to sell energy efficient furnace/air conditioner. I played his game for a little while until he asked for a credit card number. Then I began giving him fake credit card numbers. Then I told him I would call right back with the three digit security code and hung up. Poor idiot.

Called at 8:50pm I didn't pick up and they didn't leave a message.

Called at 8:40 pm. I did not pick up

It's called phone spoofing.  This is mostly done by collection agencies.  They pretend to be someone else and getting enough info from you to create an account.  Next thing you will get is a paper threat to pay something in full or go to court.  Some of us have been dealing with these bottom feeders for months and years.  We have programs that track and trace these numbers and then match them to the time and dates with the phone company. None have matched the actual caller.  They also spoof themselves as your neighbors. Advice: take your bill or some proof to the phone provider and have them trace.  If you owe money or have ever in the past, you can bet places like these will be faking themselves as someone else to get the data they need. Type:"phone spoofing" in your browser or here's a site for a start: http://en.wikipedia.org/wiki/Caller_ID_spoofing .  Everyone should be aware of these activities for their own protection. Also see: "predictive dialers" and "VOIP".