Cancellation / Complaint Help

Can anyone help me?

I rang and gave my 30 day cancellation notice early in September. Thought everything was fine and signed up with a new provider.

Only did I know something was wrong when I got issued an unexpected expensive bill for the month of October. I have spent hours trying to ring and then ended up spending hours on WhatsApp trying to resolve it. The agent was very unhelpful and said I'd agreed to One Touch Switch. I had never heard of such a thing. The agent was unwilling to do anything to help me except process my cancellation there and then which will result in me paying an additional 2 months worth of bills. I submitted a complaint and specifically asked for email contact as I have a speech impairment and really struggle to talk. I got the bog standard response of we've tried to contact you but can't. We can see your cancellation has been processed, pay your bill.

That doesn't resolve my complaint. I want the cancellation installing from the day I rang. I cannot afford the 2 months of bills they are going to charge me. From a bit of research it seems the OTS option came out on the day I contacted so feel like they've tried to force this on me but actually never told me about it. Very stressed, frustrated and upset by the experience.