Issues with annoying callers?

I keep getting calls from various phone numbers, I tried ignoring it and letting it go to voice mail for two years (They would get a message that explained that the person they're calling for is not nor would he ever be available at the number they have called, and to not call him again, then I was told to ask for a floor supervisor and have my number removed from their data base, and every time I have asked for a floor supervisor the line is promptly disconnected. I am on a National DO NOT CALL list. and these calls have gone from annoying to just short of haring. WHAT CAN I DO TO STOP THEM???