Abuse of power by a bank

I have had the most horrific experience with FNB. Last year we received a letter from the debt collectors on behalf of FNB, this amount was for bank charges amounting to R12000. We asked the collectors to give us a statement that will show an indication of how we ended with that huge amount while there was barely any activity on the account but they refused. We then contacted FNB seeking the same statement and we were told that the bank has no access to it as it was handed over. FNB then said the only option we have is to pay the R12000 and Lodge the query afterwards. Because we were so desperately in need of a new Bank account we paid The money directly to the collectors. On the 28th of February 2022 we paid the full amount to the collectors,we called them and they confirmed receipt of the payment and they promised to send an email to FNB to instruct them to update our profile so we can be able to open the bank account which we were informed would take 48 hours. Today we went to the bank only to be informed by the bank that we are still owing. What freigtened us the most was that the bank did not even know who the account has handed over to, it had to be our job to provide that information. When we got to the branch the consultant informed us that the money is still sitting with the collectors because we overpaid so the collectors are struggling to transfer the money to FNB. We asked about timelines and we were informed that they don't know how long it would take to have this resolved. FNB handed over our account without notice and even when we asked them about the name of the collectors they didn't know. I asked for a statement both the collectors and FNB couldn't provide. We took a risk of paying even though it was not written down because we were told that the account would be active in 48hrs only to be told that we overpaid so they can't transfer the money to FNB. Now we have just spent R12000 and still have no access to our account which has lost us a lot of business.