Current and Availbale

I was embarrassed when I was told that my transaction was declined at the filling station because my account was overdrawn and I could swear, through back tracing my transactions, that I could not have overdrawn my account. I was broke the whole weekend till monday when I had to call the centre to inform them about the problem. However this is becoming an entrenched trend by Nedbank, withholding transactions only to wait long enough for you to be broke, and then they make their kill in R90 dishonored fees. I tried withdrawing large sum of money and depositing the cash into my Capitec savings account and making purchases from there, to avoid being snared into R90 ****, but it is just too much work for me