I too get those duct cleaning calls.
It goes like this:
‘Hello ma’am we are calling about duct cleaning’
Me: ‘duck cleaning?’
‘Yes ma’am duct cleaning’
Me: ‘do you do Indian Runners?’
(It was at that point in time I realized it might sound racist to the person on the other end who was obviously East Indian - but I went with it)
‘I beg you pardon ma’am?’
Me: ‘I have Indian Runners, and Muscovy, do you clean those also?’
(Quiet on the other end…)
‘Ma’am we do duct cleaning’
Me: ‘yes, but what type of ducks do you clean?’
‘Your house ducts ma’am’
Me: ‘house ducks ? I don’t keep ducks in the house, they crap everywhere, messy things. But if you can clean them then I won’t have to do it myself’
‘Yes ma’am we clean ducts, would you like to set up a date to clean have them cleaned?’
Me: ‘well if you think you can handle them, I don’t want anyone who isn’t used to handling ducks, they fly everywhere’
‘Ma’am, what flies everywhere?’
Me: ‘the ducks, nasty smelly things, crapping everywhere, they never shut up quacking… hello? Hello? Are you still there?’
 
Edit: I just want to point out that when one lives in the country and it’s winter and one is bored, then one must make their own fun 

 I once had some poor guy believing I lived in a fly in community, had to hunt my own meat, chop my own wood, and melt snow for water.
Poor dude told me I needed to migrate to the city where life was easier 

 at that point I told him ‘sorry buddy gotta go, got a moose hanging in the tree out there ready to butcher - and I hung up the phone. Most fun I had with a telemarketer for 30 min ever!