Not allowing me to cancel my policy

I changed medical aids, sent them an email in November 2017 to cancel policy and they are still deducting. Sent my form to the cancellations email provided by them it keeps bouncing back. Called them numerous times still no help, I lastly sent it to both their email address and the cancellations one which keeps bouncing back and they still deducting. I want my money back from 30 days after I sent policy cancellation