Unauthorized Debit Order

I have cancelled an insurance policy on 05 October 2017, and received the confirmation via email. Old Mutual has now debited my account on 15 November 2017 which to no surprise has bounced and put me in a negative balance on my cheque account, not forgetting the fee for the unpaid item, why the hell would you do a debit at this time of the month when I clearly stated on my cancellation that the additional cover amount MUST be debited on the 28th of October 2017 for cover from 28th October - 01 November 2017 as I was moving over to a new insurance company. Who is going to refund me the bank fees which by the way is more than the fee for 3 days of cover??? This is unacceptable, I am holding on the line due to incompetency for 11min and counting to speak to someone to sort this out!!!