PLEASE CALL THE FEDERAL TRADE COMMISSION AT 1-877-382-4357 or visit their website at www.ftc.gov and file a complaint.  I just filed one myself and they told me if enough people file complaints, they will launch an investigation to get it resolved.  The problem is, not enough people are complaining.  The explanation is that you are being "spoofed" by a block of calls from a computer line and one person may pick up the call and it cancels out (hangs up) all the other #s.   They said if your phone never answers, eventually the calls will stop OR if a business answers (like a bank) it takes the number off.  
When you get the dead air when you answer the phone, it means someone else in the block of numbers picked up before you.  The FTC runs the Do Not Call list.  They also suggested filing a complaint with the Attorney General's Office.  The FTC told me to post on the Internet for everyone to please complain to the FTC so they can investigate.  PLEASE call the FTC at the number above and file a complaint.  Let's stop this nuisance.  Thanks.