Fedhealth oustading amount when cancelled

Good day, I cancelled from Fedhealth end of 2021, not using my scheme for about 2 years, not even one claim. I plan to start using my wife's medical scheme. Fedhealth started, 3 months after I cancelled, sending me constant reminders that I still owe them an outstanding amount. This amount is not even equal to my monthly contribution. I paid in advance and have the right to cancell with immediate effect.