I can relate to this. In my case I was receiving calls for complete strangers. I got the impression that the calls were intended for whoever had the number before me. Unfortunately getting the calls to stop was next to impossible since they seem to assume that their information is accurate. Had I known then what I know now, I would have sent a cease and desist letter by certified mail.
Roughly 1 hr. 40 min. ago these low-lifes called my cell phone, which happens to be a private number. Simply proves that they are using a robo-dialer which methodically dials every possible number out there, including non-listed mobile phones and everything else. Then, the computerized robo-dialer apparently left a voicemail message in the automated answering system that my wireless carrier provides whenever incoming phone calls are not picked up. (I had just allowed the phone to ring and ring when I saw the display of a caller whose number I failed to recognize.) The stupid voice message left in my voicemail said: "Dial 9 now to be connected with a live operator." That merely proves that the robo-dialer began "speaking" several seconds PRIOR to the moment when my voicemail system beeped and then began recording it!! So, the very beginning of their "sales-pitch" cannot be heard at all. HAHAHA - that's what these scumbags deserve, for operating a scam where they don't even bother to employ human personnel to do the calling for them, but rather utilize automated machines to deliver computer-voice messages (LOL). They are such jerks.