If you ring up and ask something along the lines of 'I'm an existing customer, why no good deals for me' you might get offered something like this.
You don't even have to threaten to cancel, you just ask of there's any offers for you, the 'loyal customer'
Guy at the other end said 'If you do not wish to continue your subscription to Sky movies/sports, cancellation will be very straightforward and you will not have to pay a cancellation fee... If you wish to do this you must cancel within your three month period.
So it's an offer designed to 'Hook you in' to the premium channels, but you are free to cancel before the end of the three month period, so, why not?