Supanet- can I ever leave?

foolusername

Hi folks, First post!
I was previously with supanet (for a number of years) and following my wife's redundancy contacted sky to cancel the digital TV package. This was soon after I had lost my mother, so a little blurry. They explained how they could provide TV, phone line and broadband for much cheaper as a bundle. The savings over supanet were significant plus, I was no longer tied in.

Magic!
Sky provided my internet and phone since 25th October 2010. I called the Supanet cancellations team and got cut off, so I sent an email to supanet (no reply) and filled in an online form (no reply).
Months later, my wife noticed we were still paying for supanet. We stopped the DD. Supanet have sent us an invoice for the period after we stopped paying.
I phoned billing, they told me to contact cancellations, I emailed and they told me to ring.
I made the argument that I was not going to pay for a service I did not recieve. As I saw it the service ended on 25.10.10. In fact I felt a rebate from 25.10.10 until we stopped paying was a good idea!
Today on the phone I was told that Sky had just plugged me in without getting a MAC code, so I had to pay for both providers...
The bill currently stands at £91. I asked for the account to be cancelled again today and the operative told me it could not be closed until the 'outstanding amount' they quoted was settled and they will continue to bill me month on month until it is paid!!! They told me they will refer it onto a debt collection agency.

This seems far from reasonable. I have been told all of this is in the T&Cs, of which I no longer have a copy.

Shall I write and ask for a signed copy of the contract?

Where do I go from here?

All advice gratefully accepted, but I am far from a legal expert, so please explain in lay terms!