Called today 12:21 PM, answering machine took the call. no message left.

They offered a $39 Duck vent cleaning  for the whole house.  Sound like a  good deal

But the number is CLEARLY fake.
See the "158" part? That's not a US prefix, so the call is coming (most liekly) from a computer. If I were you, I wouldn't set up an appointment with people who call you out of the blue soliciting services. It's illegal, and no REPEATABLE company would do it.

If you do set an appointment, be aware that you have NO IDEA who you may be letting into your home.

I told them I had over 12 Vents and they put me on hold  and then I hung up.   Yes this is Scam.

You're absolutely right (but I believe you meant "reputable").