FNB duplicating transactions and taking their time to fix their Mess

I did a cheque purchase online on my business account and FNB duplicated the transaction. I called them last week and the consultant who assisted did acknowledge that it was an error and he asked me to fill in a debit card authorisation reversal for (which didnt make sense since FNB did the error not me), but i did complete the emailed the form back on Monday but till now nothing had been done.

FNB is quick to charge you interest on a debit balance and they dont even care whether problem came from their side. You seriously need 5-7 days to rectify your mistakes. Fix your mess FNB.