"A reasonable suggestion - both for them and for us - is for them to insist that the robocaller sub-contractors STOP their current practices (no answer, no message) and that whenever they call a number they either stay on the line and actually talk to a person there, or, they leave a clear, brief message IDing themselves, their company ("VOLT" or "Your Community Book," whatever), and providing a toll-free "call back" number, where you can either confirm or refute delivery of their phonebook, AND - most importantly - where you can opt out from any future calls from them by "pressing 1" or something similar."
Actually, a more reasonable suggestion is that they find another way of auditing their operations. The only reason to do it the way they are doing it is to build their marketing lists for resale, there's a reason why normal businesses do not mass call total strangers over insignificant events. The costs involved in the phone-intensive method they use must exceed their total profit from producing phone books, assuming they actually do that.
Which isn't a safe assumption since this is NOT the first "confirm your PB delivery" call I've gotten and previous calls have been from a different company.
I just received a call with the same information. The guy on the other end asked me if I received a little red phone book left at my home within the last couple of weeks. I said, yes, I think so. Then he said, Is your adress still...he recited my address. I,not really thinking, said yes. Then he said is your name Janet. Once again, not really thinking, said yes. Then he saids thanks and hung up. If I had it to do over, I wouldn't confirm anything.