SHAPED - Please read my previous comments on who to contact. If your original call when you signed up was one you made into them then its the cancellations manager you need to speak to. If the original call was one they made to you then it is the sales manager you need to contact. Either way they have recordings of all calls and you should be able to demand a copy to prove you were mis sold.
The Pipex system is the one with static addresses as pipex are their own sevice privider. The pipex homecall system only rents space from tiscali and as such can not offer you a static isp.
I would recommend against you just cancelling your dd as pipex will just sell the debt to an external collections agency and it will be them who takes you to court to recover the money so that would just be a waste of your time. The only way I know of for you to get them in to court is if you instigate it.