What John says on Oct.20,2014; is exactly what I have been wondering about.
When I "Google" these unknown phone numbers on my cell phone. Then I go into a website to read what has been said about the numbers.
Is that website able to get my cell phone number while on their website???? INCLUDING maybe this website.
They in turn are then selling the numbers they retrieve to Data Publishers (i.e.: telemarketers and scammers).
My feelings for myself is that MY cell phone number SHOULD be wholly PRIVATE to anyone but my own contacts. And when I find an app that "requires" all my PRIVATE data: I do not download it. An Accuweather app I recently had; when it came to updating, "required" ALL kinds of my data. I not only unloaded it; I "force stopped" it; then cleared the cache and data.
My landline if not "unpublished" is not private: if I choose not to pay for being unpublished.
In either case I DO NOT ANSWER PHONE NUMBERS I DO NOT RECOGNIZE PERIOD.
Same nonsense about a "$100 reward card" from an unidentified website that I supposedly visited. I hung up within 10 seconds. I don't believe that they are associated in any way with booksellers or amazon. If there were $100 rewards for spending $35, every commercial website would go bankrupt. As others have said, SCAM! Don't bother to answer.