Deceptive balances and unauthorised deductions

On the 30th January I deposited an amount off R8000 in my standard bank prestige account the balances updated immediately and reflected the monies.the following morning R5000 had been taken off my account.I have always maintained my account and made regular deposits to cater for these balances and my overdraft.I called Standard bank and as usual there was nobody that could provide me with an answer.the lady told me that my account was overdrawn by R5000 which was NEVER reflected on my statements.I logged in yesterday and the balances showed I had the 5000 available.this is highly deceptive and I am not sure were the error lie but I am sure that I would not have went over my account by R5000 and why would Standard bank not notify me if this being such a big amount being overdrawn.the statement on my cellphone banking and Internet banking never reflected I was over by that amount.it is now Sunday and I have to wait because nobody at the call center can assist.thus is absolutely ridiculous and I will be taking this up even further.Please rectify this immediately as this is unacceptable