http://800notes.com/Phone.aspx/1-877-273-3495
Debt collector using local Denver area phone number on Caller ID, but asks you to call 877-273-3495, which is NCO Financial.  A deadbeat had this number years ago, and still uses it for credit, so I get these people calling me all day. For years. I have NO debt to anyone, so I usually just block these numbers.

It would pay you to deal with these the proper way since you have a cause of action against them.

You need to send them a certified, return receipt debt validation, cease and desist calling, or "not me" letter.  You also need to report them to the proper agencies to which I have provided links to.  Then you need to go out and get a consumer lawyer to sue them on a contingency basis (no money out of your pocket) and let them pay you for the harassment.  If everyone did these three things, these crooks would be bankrupt and we would all be the richer for it.

Read up on your rights here, get template letters to send and also make a complaint at this government site: http://www.consumerfinance.gov/

Also file a complaint with your State Attorney General's office.
List of State AG’s offices:  http://consumerfraudreporting.org/stateattorneygenerallist.php