Delayed Refund and poor feedback

I had cancelled the medical aid in January 2017 but the medical aid kept on deducting money every month unit May 2017. I reported the matter but still till today the matter has not been resolved. Driving every week to do a follow up but still. What does one do in a situation like this? I have submitted my bank statements 3 times as per their request but every time when they should deposit the money they say the account number is incorrect. It's very frustrating and inconveniencing. I'm very dissatisfied with the service. Please assist. Thank you.