Intially Ntl told me there was no contract for my Broadband. Then they said I had a 12 mth contract. Do I pay?

In March we took out Broadband with Ntl. In July Sky offered for free with a BT line. In August we cancelled the Ntl phone service and asked if we were in a twelve month contract (twice) no was the answer both times because of the lenght of time we had been customers. In October I phoned to cancel the BB.Office closed but the request would be posted and cancellation backdated one day. The next day I phoned to cancel and was told that I had to give 30 days notice. When I requested it start from the previos day I was told no. When the supervisor came on she was very bolshie and insisted I was subject to a 12 month contract and there was 6 months still to go. I wrote cancelling my BB with them enclosing a cheque in full and final payment for the next 30 days. Ntl have now written back saying they will not process my disconnection until we agree a final settlement figure. Do I have to pay anymore or is the advice that I wasn't in contract legally binding on Ntl?