Discover Medical aid claw back claims from their clients

I got retrenched by my employer in 2019 and had to cancel my medical aid before the end of the term that was only left with 3 months. During the time of my membership my funds were depleted and I paid close to 2 thirds of what was my allocated benefits out of my own pocket. I was not hospitalized either none of my dependents were so I paid more to the medical aid that than what I got from it. Later I rejoined the medical aid when I got another job, they accepted me as their client and I took more products from the company such as life insurance and short term insurance. I pay close to R13000 per month on my product portfolio to the discovery company. They have handed me over to their attorneys to collect what they call a claw back charge of R6000 from me for the cancellation of the medical aid. I have called them telling them that I don't owe them anything and despite I am their client on other products. R6000 is not going to bankrupt them. I have called their contact center and have written to their broker to them to give them an option to choose if they want me to pay the R6000 or that I take my product portfolio away from the no answer from them. There has been no answer they continue bullying me through their lawyers. So much for their so called customer care with the Discovery company. Right hand does not know what the left hand is doing.