Endless phone calls

A week ago we got the first phone call and the caller asked to speak to my father.  When I tried to tell them that he is deaf they hung up on me and since then I have recieved three more calls, two today!  I am on the the state and national DO NOT CALL list but that doesn't see to matter.  I want the calls to stop.  My father has multiple health issues, including Liver Cancer and Congestive Heart Failure and these calls always come in at a point when we are trying to rest.  I'm calling our DA on Monday to see what we can do to stop this.