Download the "Disconnect Ring Tone" and play it whenever you get a call such as this. Note there is a pause between your picking up your phone before someone answers. This is the computer determining whether it has reached a valid number. If you play the disconnect tone, the computer automatically removes you from their calling directory.
I have received probably 20 calls from them, after being on their do not call list since day 1, just got a new cell phone, and they have that number already... put on do not call list, lets see if i get any more on my cell...