This ploy is all simply anecdotal hearsay and never actually works. It is the classic “I have a mate who …… “.
I called them a while back and said I was leaving because of costs. He tried to sell me a full price upgrade to Sky Q and then finished off with asking me to confirm a date of cancellation.
You may be offered a small reduction in set-up costs however after a period of a few months the prices all go up.