running around in circles

I had a car rental with avis, now avis says once rental is over, the amounts were simply placed on hold and the bank should automatically release them once the rental is over, meaning my balance will increase but this wont show on my bank statement. I have called the call centre countless times, lastly speaking to a Zweli Ma***u, who was so rude and unhelpfull, i need a manager to check him out as he was most unhelpful, his tone was rude and unhelpfull that if you listen to the call, i decided to end the call myself as he was literally screaming at me on the phone. If funds were released and my balance was suppose to increase, why is it then no-one can show me that my balance increased on certain dates. im utterly dissapointed in FNB. i need a comptent person to call me and explain to me wrt this issue, as avis tells me that the bank simply put the funds on hold, and the bank is suppose to release them. another reference i have is *** <div><br></div><div><em>(Supplier name changed from Fnb Insurance Brokers to First National Bank by Hellopeter.com)</em></div>