Len,
I have the same issue. I sell stuff occasionally on CL.
After playing the game and asking them to remove me from their call list, one nice individual who sounded like he was calling from the Philippines, told me, "I don't give a sh*t about your laws! I am not even in your country!" So, I gave that up and started putting the phone down after answering and blathering on about, "... how stupid can these people be because they won't take me off their call list..." CLICK. Problem is, their computer identifies you as an ANSWERER and it doubles the call frequency.
My wife never turns her ringer on. If I call her, I have a 10% chance of getting her. But, because she never answers robo calls, I went back through her call list and her frequency of robo calls was like a quarter of mine -or less. So, it looks like playing with them only invites more calls.