I used to cold call businesses and I have to say it would have made my day to have some of the more inventive ways of dealing with my calls than the usual "oh ffs, will you just feck off and die!" (Yes I got that SEVERAL times in my first day!!)
I get several cold calls on my LL, when my SIL lived with us for a couple of months I got home one day to find her having a rather...odd conversation, along these lines (I'm parrot-phrasing here as I can't remember the actual words)
SIL: oh yes, I have to say I love yoghurts
Caller: can I speak with ms 84 please
SIL: yes you can, but first, I just HAVE to tell you all about when I went shopping today, could I find what I needed, could I buggery!! How hard can it be to find a decent bloody vibrator?? Have you had that problem
Caller: erm...
SIL: aw come on, I'm sure you must have bought one once??
Caller: click
I was in hysterics!!
Personally, I'd say the whistle goes too far, however, if the usual "I'm not interested" etc, haven't worked then I can see why people resorted to such tactics
Would like to point out that the companies I have worked for have all been legit! :)