I usually have some response if I tweet the company who cold calls (eg Abel and Cole, charity chuggers who INSIST on calling after 5pm - 5-7pm is bedtime routine and then I'm not interested in opening the door to uninvited people once the kids are in bed, LoveFilm who had a run of being really aggressive and apparently "funny" with their approach - I'm a Christian and was appalled when I opened the door and was asked, Can I talk to you about the Bible and then, oh, just joking, I'm from LoveFilm) - but that doesn't work with the sponge sellers