Do you want to know whose been calling you? If you're in luck, someone else might be getting the same calls & reported it. To whom you might say. Well, the site is called "WhoCallsMe". It is a database site for Reverse Phone Number Lookup purpose. And it is actually a users supplied database of any phone number from all sorts of people.
"This is a user supplied database of phone numbers of telemarketers, non-profit organizations, charities, political surveyors, SCAM artists, and other companies that don't leave messages, disconnect once you answer, and simply interrupt your day. If you received a strange call, unwanted SMS message, or just came across a number you don't recognize and want more information about, most likely you are not the only one. Search for this phone number to see the reports of others. If there are no reports yet, leave your comment to start a conversation."
Well, now you know. I've tried some numbers from local companies & they're listed too. Their customers were annoyed enough to list down the phone contacts in here :)