I too havebeen 'slammed' by Pipex. I was a BT landline customer up to a couple of months ago. I then started getting bills from Pipex, as I to my knowledge wasn't a customer of theirs I didn't pay the bill. I have now been cut off by Pipex. I have spent many minutes talking to people in India (I presume) without gettting any sense. I have made a complaint to Ofcom and Otelo. I have sent a letter to Customer Liasion (?) but got no reply.
I also intend to sue Pipex unless I get an apology, my bill written off, a confirmation that my credit rating won't be effected and compensation for the stress, inconvenience and expence caused me.