I know, I have had the same problem. They call multiple times per day. They don't respond when you answer and when you call back you get an answering machine!
I have received 10 calls just today, when I answer and say "hello", no one there. However, when I answered the phone, but said nothing, they asked for me by name. When I asked who was calling, they said something like " Mathis Survey". I said no thank you, and hung up. Still continued to receive calls after that. Time to get the whistle out....