If I get them I generally just put the phone down immediately, or I'll wind them up asking stupid questions about their qualifications. However, my nana has had a few recently who've been super aggressive about it, I told her not to do anything they say and to call me if she's unsure, but apparently saying 'no' and putting the phone down gets you repeat calls if you sound like like a good mark.<p>Edit: I'll point out, this happens in legitimate call centres as well. I worked for a fairly well known a credit card company and left not long after I heard a top seller say "Focus on old people, scare them enough and they'll always buy".