This number called my office several times over the last week but never leaves a vm.  Didn't find anything about the number in web searches so I called it back.  An automated system answers and says "You have reached Swan Energy. To be placed on the Do Not Call list, press 1, or to reach the receptionist press 2."  I pressed 1 and the system said "Thank you, goodbye".  Then I called back again and pressed 2 to see if I would actually talk to a human who could tell me what they do, but it went to hold music until the system said "The person at extension 5 is on the phone", then went to a voicemail tone.  I suspect that now that I've called them back and requested DNC status I'll probably get even more of their spam calls, unfortunately.