FNB Credit Card - extreme delays in refund amounts

Hertz Rental Car loaded R8247.00 on my FNB credit card on 27 Dec 2015 as a deposit but refunded it on the same day and showed me proof thereof. FNB has STILL not processed the refund and it is STILL not in my credit card! On the same day Hertz also loaded and then refunded an amount to my ABSA credit card which was refunded and reflected within 2 days. I have lodged queries and complaints at FNB but they only make promises to investigate but does nothing. What does FNB do with peoples's money??