Virgin active forcing debt on me that i shoulfw not pay

Have an absolute disgust with this company and they putting me through hell.. A couple of years ago i had virgin active contract at somerset west gent centre. Upon retrenchment at work i opted for a way for them to reconcile and cancle my contract but they insisted i pay. Eventually i paid the full amount in cash and things was done. A few years down the line i decided to join again. Paid the sign up fee and i was in. After two days i couldnt get in. They informed me that i have a debt of 5000 rand plus. And i cant understand this. I phoned there customer care and they said i have been handed over..now im ****ed i dont know nothing as according to my memory i paid.. They wanted proof..who would keep a proof of something they paid finsh two years ago.. I phoned mbd and on there system showed i paid but there is a balance that is increasing.. I requested a paid up letter but i was rudely rejected by saying that i should pay first. Since then ive been getting calls that i should pay the amount which has now raised over 6000 rand im sure.. Im disgusted by this place as im now being forced to pay something i don't even have to pay.. A debt has been forced on me.. I am a young adult age 24 how am i going to handle this.. All i want to do is gym as the place is nice and convenient for me. But im disgusted by there actions. The staff is nice everyone tried to help me the best they can but this is utterly disgrace. Ill probably never be able to gym at a virgin active again