You can register the number they called from (even if it doesn't appear to be legitimate) to the donotcall.gov list.  There is a Federal investigation going on now for the credit card interest rate and auto warranty scams.  Use the following link:https://www.donotcall.gov/complaint/complaintcheck.aspx

Fishing calls to my business line, and very poorly run at that.  Don't think they have a lot of people.  Bogus number, appears wholly automated - very persistent.  These morons need to go away.  Suspect they are from one of those "lower my interest rate" web sites operating from Canada.

I called Verizon and they told me unlawful calls can be reported to 1-+1 800-257-2969.  I don't know what they can do immediately if the number is bogus and keeps changing, but if enough people report it there will probably be an investigation.

May 10, 2009 11:30 am US/Pacific Probe Demanded For Phone Spam CallsN.Y. Sen. Schumer Wants End To Robo-Calls Trying To Sell Fake Auto Warranties

You can register the number they called from (even if it doesn't appear to be legitimate) to the donotcall.gov list.  There is a Federal investigation going on now for the credit card interest rate and auto warranty scams.  

Use the following link:
https://www.donotcall.gov/complaint/complaintcheck.aspx