Received (detected) two calls from this number. In two consecutive days, at approximately the same time in the morning. I picked it up both times, but they did not answer... Called back and heard "not in service" recording.

I am receiving, as many of us, similar calls, when the caller does not answer. Sometimes I can hear or feel that someone IS actually listening (slight background noise, etc.). You might only guess whether it's faulty machine/program, careless caller, just a wrong call or something worse. What if they came up with a next evil marketing idea of, for instance, "quiet" (statistical, demographic, etc.) identification/research of, say, who-is-at-home and what-time-of-the-day? And this is just an assumption that they are intrusive, but legal (sort of). But what if they record people's voices? Or use the system for some other dirty purposes?