Listed without knowledge

I signed a contract with the gym, the contract did not specify the term of the contract! To my surprise after a few years when I apply for car finance, I found out I have been listed by Gym Company for more than R6000.00. How on earth did they come up with this amount and why was I not informed about this?? This is a pathetic GYM and I demand a copy of the contract I signed or I will be going to my lawyer.