Asked if I could sign up for 3 months only

I went to the Randburg square branch and asked if I could sign up for 3 months only. The gym official said that it would be possible and that I just needed to give notice before the end of the month. When I tried to cancel the gym membership, I was informed my contract was for 3 years and I could not cancel. I did not even know the contract term was 3 years. I only asked for 3 months. Now they want me to pay the balance if I want to cancel. I was not signed up for what I asked for.