Incorrect Charges on My FNB Cheque Account

Incorrect charges on my Bank Account , I notice an incorrect charge on my Cheque Account and when i queried with the Bank i was told that my Account was overlimit hence the charges...My Account was not overlimit and upon following up i was given a Reference number that the amount will be reversed into my Account within 2 -3 working day...Im currently on Day 6 and the amount has not been reversed and follow ups with the Bank is not yielding any results