Over debit

I have a policy with Miway for my 2015 Honda Ballade at a premium cost of R1400. On the 26th May, Miway debited my account to the amount of R2900. I then called Miway who were then going to credit my account within 7 days. Three weeks later I still have not received my money from Miway. I phoned them back to followup with my refund on the 11 June, I was told it wasn't processed the first time, but they will process it and it will take seven days. I asked to speak to a manager and I was put on hold for 12 minutes, eventually I hung up. This is the 2nd seven days that I have had to wait for my refund. At this point my bank account is in excess and my bank is going to charging me penalties for a negetive balance. Now I have to carry the costs of Miway over debiting me. All I wanted was my refund but now I want my money and I want to cancel my policy.