Standard Bank unjustly enriched itself by charging unwarranted charges

I opened my cheque account with Standard Bank Jeppestown in January 1972. The service was perfect for more than 45 years. Then things changed. While I was in Botswana in 2018 a home loan debit went through causing an R 18 overdraft. The debit order was for in excess of R 3600. They bounced it ! Now recently at end of March my rent was late and an SABC debit for R 28 was bounced and I was charged R 60. Then their own card debit order for R 48 was bounced and they charged R 60. I wrote to ********** and asked them to reverse the charges because in my opinion their action was immoral. They wrote back and told me that when my account overdraws it causes reserving requirements by the bank. I rep**** that they were talking hog wash because they caused an overdraft of R 120 but if they paid the 2 items it would only have been R 73. Not large enough to cause a run on the bank. Of course my email was ignored. Then a few weeks later I put a stop payment on a debit order which I had cancelled with the company. That company explained that their computer is programmed to double up a debit order if it is returned unpaid. So I put a stop payment for the doubled up amount. Low and behold they bounce it and charged R 146. I wrote and explained the situation only to told that had to get the date and amount correct otherwise it will bounce. I had all the info spot on but still no refund. Therefore in my opinion the bank had unjustly enriched itself by R 266. So I closed my card account which will result in a loss of revenue to the bank for the rest of my life. No too long from now I will close my 47 year old cheque account. All for the sake of a horse shoe nail the battle was lost.