Gym contract

Hi, I cancelled my gym contract from Planet Fitness in 2014 from planet fitness. I even called and emailed the cancellation documents. They then sent my account through to Saya Recoveries stating that I owe them money. Each time this amount accumulates interest and they call me for payment and say they will blacklist me. I am currently unemployed and still a university student I have R200 to pay them every month. I try pay when I can, but its a challenge. I really feel unfairly treated and harassed by them.