It's easier to cut off one of your own limbs. I also got the sales speech when I tried to leave. In the end I told them I no longer had a computer and was moving abroad and so the bank credit card they took the payment from wouldn't exist. I'm sure it's easier to leave the mafia.
Switched to tesco.net for dial up who were great and I'm now with Pipex for broadband who are great as well.