Like most who have posted here, I, too, have received numerous unwanted calls from the number identified as 720-452-5527 on my cell.  I registered some years ago on the Federal Do Not Call list.  In response to these unsolicited calls I have texted back to the number describing their behavior as harrassment and asking them to cease calling me.  Happened again this morning.  I suggest that all of those who are receiving these unsolicited calls file a complaint report with the Federal Communications Commission.  I did this last year with a company that would not stop calling me no matter what I said or asked or texted.  It actually resulted in a series of actions that ended the calls.  So I'm going to do this again.  Here are the complaint instructions.

Go to this page: http://www.fcc.gov/encyclopedia/do-not-call-list  and scroll down to the section "How to Complain."  Instructions are provided for filing a complaint:

You can file a complaint by telephone to 1-888-CALL-FCC (1-888-225-5322) voice or 1-888-TELL-FCC (1-888-835-5322) TTY, by fax to 1-866-418-0232, via our electronic complaint form, or mail. For the FCC to process your complaint you must either fill in the electronic form completely or otherwise indicate:

your name and address;
the home phone number where you received the solicitation;
identification of the individual or company whose products or services were being advertised or sold, and any phone numbers included in the call;
a description of the call;
any phone number provided to allow you to “opt-out” of future calls;
whether you or anyone else in your household gave the caller express prior permission to call;
whether you have an EBR with the caller (specifically, whether you or anyone else in your household made any purchases of property, goods, or services from the company that called, or made any inquiry or filed an application with the company prior to receiving the call).