Those of us who really don't like to say 'no' can always say 'I need some time to think about it'. A pushy salesman will almost always say "But we need to know right now!" or some such thing. But that puts him in the wrong, and allows us to show anger and snap, "Please don't rush me! I don't like to be rushed. It's rude to rush me! [mutter, mutter, mumble] Don't rush me!" and go off into a bit of a tantrum, if you can manage it. Another ploy is to say, "I want to check this with my son/neighbour/friend. He's an accountant."
Scammers don't want to meet accountants, I assure you. I get occasional cold-callers phoning to persuade me to invest with them. I say "Thanks, but I make my own investment decisions. I'm an accountant." Maybe they think I'm a fellow-scammer and hang up out of professional courtesy... But they do hang up!