I don't have a sign up, but I don't have any trouble saying no thanks politely enough - they always accept it. Maybe it's because I'm quite tall and dds say I can look quite scary when I put my mind to it!
However I made the mistake a few years ago, when a double glazing salesman from one of the very big firms, came to the door, of asking him for a quote. We were actually in the market for some new windows at the time, so I thought, might as well.
Of course I should have known better. He quoted some quite ridiculous figure, only to add almost immediately that just for today, he could offer me about 50% off - but only if I signed here and now, in other words.
I could not believe he was employing exactly the same tactics as DG salesmen we had in over 30 years ago. 50% off my a*se - why can't they just give the proper price without this stupid charade?
I declined, of course, and when someone from the company later phoned to ask why I hadn't ordered, I told her, adding that such stupid and patronising tactics would put me right off any company. Particularly theirs.
Incidentally we had exactly the same tactics from someone (again a big company) who came to quote for a whole wall of fitted wardrobes. He was only interested - and would only apply the 'discount' - if we signed there and then.
There was actually nothing wrong with our wardrobes, except that they were horrible white melamine with equally orrible handles.
Next time dh went away on business for a week, I emptied them, got some melamine paint and some nice new handles from Wickes, and gave the whole lot a makeover.
Took me about 3 whole days, but cost about £65, instead of the £3 or 4K the bloke had quoted, even with the discount. ?