Shocking Service

We have a Telephone account and a ADSL account. We requested the ADSL to be cancelled more than a year ago. Every month we get an account, it has the ADSL billed. Then we call and they credit us. We completed and emailed the cancellation form at least 4 times and have followed up constantly. We have not had the use of our landline for the same period, because the account is not paid... but yet they continue to bill us for the ADSL line. When we call, we get through to very friendly people, each time someone else, who then promises to sort out the problem and they provide reference number after reference number... but unfortunately we still have a bill showing ADSL and Interest and We have NO ADSL, have not used it or had it and likewise do not have a landline to use.