Refused refund on a double billed account

I have a personal loan with Nedbank and tgey made 2 debits in one month.I requested a refund on the 01/07/2015 and was told i will wait 7 days. I phoned for the follow up on tge 7th and was told a refund was declined by Natasha Morgan whom I wasnt able to speak to as they said she doesnt take calls. Other debits that were supposed to go through did not because there was no funds in my bank due to nedbank's double debit. I was charged R90 each returned debit through to Nedbank. i was not even told the reason for my refund refusal