Not Allowed to cancel membership

I joined Gym Company around March/April this year, then got diagnosed with chronic disease around June and unfit to gym. Now I tried to cancel the gym as it was a month-to-month contract, but some lady said I had to pay the outstanding amount. I paid the outstanding R400, then she turnaround and said there is a 3 months notice. She still has not sent me proof of cancellation and dragging the process. Can someone please assist me with the cancellation as this was a month-to-month contract but now I am being dragged with a 3 months notice period.