I called the number back this morning. Their pre-recorded message for the legimate company says that a telemarketer has spoofed their caller ID and has been calling "at inconvenient times". The message further encourages callers to contact their local phone company to see if the number can be traced, and to report the incursion to the FCC.
I know for a fact that this can happen with software out there. It's just as easy to spoof a caller ID as it is to spoof a URL. I feel sorry for this company. They are a victim here too. I imagine they had to put that recorded message up to keep their receptionists from being bullied.