Unfair billing

I received an email from Virgin Active saying that if I want to terminate my contract which is coming to an end I need to inform them before 30 November. When calling to end my contract telephonically before 30 Nov they informed that they will be charging me prorata saying I was supposed to cancel 20 days in advance. I explained that I received contrasting info in the email. When I asked who I can contact to dispute this further, I have not yet received a response.