It's the old clean your air ducts scam.  If they are violating the do not call list, I wouldn't let them in your house.  And generally, the deal is that the come to clean your air ducts but then you need "other work"

5/23 13:35  No ID but fool stayed on phone long enough to listen to answering machine and then say "hello" four times.  The longer this goes on, the more I realize how many complete idiots there are around us!  Give me a break, already.

5/26 11:46 And again, even holiday week-ends  provide no respite.  The only saving grace this time is that the fools didn't bother to say anything, just stayed on line long enough to register as message with background noise.

6/03 16:02 Never seem to give up, as all other calls before, no ID but long last "message" of boiler room noise.  No actual message, only noise.