Honest mistake decreasing overdraft-now in arrears

I phoned the FNB call centre wanting to find out if they can set my account that my overdraft decreases every month on 15 May. The lady said I must do it online. I went on my online banking and ACCIDENTLY put in the wrong amount. My available balance now shows R-6100.00. I immediately phone the premier banking number and explained to the lady, this was on Friday 15 May 2015. She said she can see that it was a mistake and will lodge a query that FNB just reinstates my limit the way it was and then I can decrease it the way I want to. Till today, 19 May 2015 - NO ONE has contacted me. I have followed up 4 times and every time the centre just says that they are still busy with it. When I spoke to another lady this morning she says I now need to re apply for a new overdraft - that is ridiculous. It was an honest mistake. The issue now is that my bank account stands in arrears and when I do receive my salary my debit orders will be returned. I need this to be resolved asap.