I am in the same boat as you. IE. being ripped off for a phone line that doesn't work.
As far as I know it is still an "obligatry condition" of receiving there "clunky" DTV service.
I think the reason is that the company is so mismanaged that they can't make any money from their TV service and so "force" us to subsidise it to the tune of an extra £11.00/month.
Maybe you could strike a deal with retentions/customer relations, trouble is they are so snowed under with people cancelling that usually you can't even get in the queue to speak to them.