Money withheld by FNB for Avis car rental

Please help, I hired a vehicle on the 27th January 2018 through Avis and my money was withheld for security purposes, after 3 visits to the local branch I was told that I need to fill in a 14 day dispute form which I did and I got the results on the 10th of February which indicated that the money was released on the 26th of February, we went through my statement together with the branch ladies and we could not find any increase in my balance of such an amount. Then I logged a dispute on the same day of the 10th which till today is still not resolved, I keep calling the help line holding for long time and everyone goes through my account trying to establish the exact day that my balance actually increased with such a reversal with no luck. This is frustrating, time consuming and also costly as I hold for a lengthy of time as well for this people to actually come to my assistance.