Billing ans cancellation nightmare

I am having such a horrible experience cancelling my fiber line due to a move. I have a reference number SR***. Firstly, I changed my banking details 3 months ago but they have not been debiting and I have received no notification nor have they suspended the line. Now that I have to cancel the fiber I am being moved from pillar to post, and I am being expected to pay up to the end of November as well. Why do they keep a line active without receiving payment or notifying the client, then they tell me they can't suspend services as well because I'm in arrears. They are claiming that my banking details were never changed but when I asked the call centre what banking details they have they confirmed the new ones. So in essence, they can't cancel the contract or suspend the services even though I am not using them. WoW