Virgin active is unfair

I have been loyal to virgin active since my start date even when i was not fit to go to the gym for over 12months i still payed,then whn i wanted to renew my contract their staff member told me there is no need cause if i decide to want to leave the club i dnt have to cancel i can just leave without having to send a letter or anything then this year i decided to leave stopped paying and entering their facilities, now they telling me i owe them,if the lady at the club did not say i can leave without informing them cause those are changed rules as their contract states it will be amended from time to times i would have notified them,so now they want me to pay what i havent used,i feel its very unfair for me