another nuisance one is The Foresters ,a gentle voiced oldie calls up mentioning disabled children, I dunno if its in the same league as the blue light but they sure are pests
I find its best to simply say "I don't do that sort of thing"
or "im skint,fiscally challenged ,no money here" they usually follow it up with you can pay later,6 months later,at that point I get nasty .