Being charged for amount not mentioned on contract

I've been member of virgin active from January 2014 on 24 months contract. Now that I don't have a car anymore to access gym, I would like to cancel my membership contract. I called to request cancellation procedure and I was told that I will have to pay 40% of remaining contract. I requested my copy of contract to verify this and there was no where 40% was stated. I called again to request their full T&Cs, still there was no mention of 40% cancellation fee. Checked their legal section on website, still there is no mention of 40% cancellation fee. How can I pay for something which I cannot see in writing? All I want is to see that clause in writing.