You can also answer the phone (when it shows not provided, or the like) with "Sheriffs Department, how can I help you"?. We've done this to a few, and never heard from them again.
They do not honor any "do not call" list. They are a call center in India. Here is a harsh suggestion, if would you like to put a complete stop to these people? His is a harsh way to do it but first buy a police whistle, then when they call you and ask for your name say "just a moment" then take your police whistle and blow it full blast in the phone. It's severe, but that will put a stop to it. Please don't do this to a fellow American telemarketer that is just trying to make a living. This happened to my wife when she was trying to generate leads for Medicare supplements. She has not gone back on the phone since that has happened to her.