Fnb account adjustment never explained to me

A ********** cheque of R14500 was deposit to my business account, the bank made an adjustment on my account to the value of that cheque resulting in excess in my account. I have never recovered from that situation as I couldn't deposit any money to provide for my debit orders, I had to stop using the debit card machine for this account. I was never given any explanation for the adjustment which happened around month end of May, my debits accounts bounced, bank charges kicked in and it was chaos in my account. At the time, I had communicated with the bank's customer service, my account manager, been to my branch without any success. When the adjustment was ultimately cleared, I was in excess of over R9k. I suffered as I could not use the card machine or make deposits, my account was in a healthy state before the adjustment by the bank. I want to start using this account and card machine ASAP. The bank needs to look and resolve this account for the situation I have been put in. Ref number 694195NF was issued by FNB for this complain. Again, to this day, nothing was explained to me after all, my account manager could not be able to explain that adjustment nor the customer service.