A site that I find helpful that I wanted to be kind enough to share is
http://800notes.com.
Apparently, it used to be for just 800 and other toll free numbers, but now there are HUNDREDS, maybe thousands of numbers on there.

You can read comments from people who also got a call from a particular number. And of course, you can add your own without registering with the site. It helps you see who these people are, even if you never plan to answer the call.
So if you get these calls, if you look it up here or even elsewhere, there's a
99% chance that a lot of other people are getting calls from them too.
Portfolio Recovery is a collection agency hounding innocent people with their calls by using outdated info.
And I just HATE "Unknown Caller". It kind of reminds me of a horror movie. Calls from "beyond the grave" always say "Unknown". LOL Or like if the phone is disconnected in a horror movie, but it rings anyway.
I've gotten too many calls to list the numbers here, but everyone be careful. Also, don't press any keys. Only a human can do that, and that validates the number to them. Like if it says Press 1 to be removed from this list, you might actually be "adding" yourself to something else without knowing it.
Like I said in similar thread awhile back, the only way you can be sure of who you're talking to in cases like this is if YOU initiated the call. I've gotten calls that "Time Warner". It COULD be them, but it could be a phishing scam. Besides, I don't want to talk to the cable company anway. They just want to sell me more services I don't want.