10:17 A.M CST on September 13, 2016. I didn't answer, and the message they left on my machine was your typical automated message promising that they'll clean my furnace and to press "1" if I was more interested in their offer, "2" if I wanted off their list.
Do yourself a favor, folks: You're better off blocking these creeps...or, if they've been harassing you, turn them in to the FCC.