Incompetence in closing medical aid scheme

I moved to New Zealand from South Africa in September 2015. At the start of September I phoned Discovery to cancel my health scheme as at the end of September. This was apparently logged on the system and done. However, in early October I noticed my account was debited for an October premium i.e. the request was not completed. I phoned Discovery on 5 October 2015 to query this payment and make sure they refund and close the medical aid scheme. They noted their error and promised it would be remedied and refunded. It is now 29 October, and nothing has been refunded into my account. I am ow concerned that this hasn't been actioned once again and the November premium will soon be deducted. How many times do I need to make an international call to try and fix their self admitted mistakes? Really not happy.