FNB Transactions Discrepancies

I am very disappointed with FNB, since last month I have been seeing strange deductions from my account. I keep my money from Savings pocket and whenever I want to do transactions I deposit the money and run with my transactions. On several occasions my money got deducted as if I made transactions without money, I know that my account cannot go overdrawn. So every after 2 days there will be a negative balance with the message that shows " #ITEM PAID NO FUNDS 4 ITEMS ON 25/04/". I called consultants but no explanations,I keep getting this every 2 or 3 days, when I do transaction. I heard that my colleagues also are complaining about this. FNB do something otherwise you will loose clients.