Male voice, very brusque, calling in an intimidating way, insisting we sign up for "cleaning the furnace.
When he was asked to put our number on the do not call list he said, "Let's get this done with" and insisted on doing an on-site cleaning.
female voice, saying she was calling to offer chimney cleaning for oil and/or gas furnace. I told her we did not have oil or gas. She replied '"liar, you are a liar" and hung up on me.