Worst service ever

Hi , im was with One Plan , and I was cancelling with them , because I was switching over to another medical aid , I phoned one plan, stating I want to cancell, i wrote a written letter that I was cancelling , I got an email confirming they got it, then I had to pay a penalty fee just for cancelling, and they said my last debit order would be end of November because from the 1st of January im om my new medical aid. What happend , 1st of January 2018, they took of another debit order , after phoning , nobody could help me , and all response I got was , its just the way one plan does dings!!! Really poor services and I would warn people to stay away !!! Im going to take this matter further , seeing how I have all the proof