Are you in the National Do Not Call Registry? www.donotcall.gov
Some telemarketers still get away with it, but it works pretty well for me. Keep on not answering or calling back, that also works in the long run.
Answered call after one ring, but no response from caller at other end so I hung up. I guess I'm now on the 'hot prospect' list and should expect more calls as that list is sold to other unscrupulous marketers.