Just received a call, I don't answer calls from numbers I don't recognize and of course there is no voicemail message. If it's so important, then leave a voicemail message guys! Seems the only thing consistent with these callers is the time of day they call. I have received the same Unknown Caller from Chicago, IL around the same time M-F, but the number keeps changing. I'll keep adding the new numbers to my blocked calls list, eventually they have run out of numbers......