Nedbank is a *****

So we paid my wife's loan off at nedbank but 1 of their staff decided they can go onto my wife's account and do a reversal on the payment/account nedbank did not even call us to see if we did the reversal or not so month end comes they debit my wife's acc and we call the bank to find out why did they debit the acc when she paid it up. They said there was a reversal on the acc to go and do some digging 1 of their head office people did the reversal for no reason now that we are complaining and want answers on why did he just go on to the acc and do that nobody is calling us with feed back our lawyers said we can sue them but for now we need answers is it common for the banks to log onto a person's acc and do what they feel they want to do to a person acc?