Double debit

I have cancelled a funeral policy and upgraded to a new one. Last month Standard Bank debited my account twice, one for the new policy and one for the policy that is meant to be cancelled. First time I called to enquire I was told that the policy will be cancelled and I will get a refund. This did not happen and again they debited twice this month. This is highly frustrating and causes and inconvenience because I cannot honour my other debit orders. Please assist in resolving this and be sure to send me proof that cancellation.