Inability to process transaction timeously

Hello Peter, I need your helpadvice. I've been a client of NedBank for over 4 years and things were OK until I switched to their Gold cheque account. About a few months ago I would get sms's that my account was in arrears and over drawn with penalty fees imposed. Thinking that maybe I had unknowingly agreed to an over draft facility, I inquired only to find that what actually happens is due the delay in communication and transaction between the bank and their suppliers (shops) the transactions actually never go through to the bank or the shops take a while before they do their banking resulting in the late processing of the funds which by then tends to find my account empty resulting in the over draw. I asked the bank why they don't at least reserve the funds,keep track of how much I spend and decline the transactions should I exhaust the funds as would be expected but they can't answer me and keep telling me about how their suppliers don't do things timeously but then whose fault is this? This month,I had concluded that I'm switching banks but when I tried to do that, I was told that I'm once again in arrears from transactions that happened on the 16 and 18th even though I had fnd