Some companies check the do not call list for numbers they can then phone - one called told me they got my number from the do not call list. Any company can access it to see if they are allowed to call you.
You may still get calls even if you are on the Do Not Call register. Political polling calls are not covered under Do Not Call, so telemarketers and spammers can get around the restrictions by asking you a political question. It will cut down on the number of calls you receive, even if it doesnt completely prevent them.
A very reliable online site like USpopularnames.com will let you experience visiting a dependable web-based community. In case you need verify a call using a reverse lookup directory, this website lets you complete the process. Likewise, you can post your comment and let other people read it.