Standard bank is the worst

So a few years ago I closed my standard bank accounts, probably 5 years ago. To my surprise I receive a call from them telling me that I have money in my account. all excited I go to the bank only to find out I owe them over R700 for service fees accrued over the years. How is that even possible when my last encounter at the Nicolway branch they paid out my savings and 'closed' my account. A weeks ago I was advised that I'm to pay R766 by 1st of August to settle the account, I agreed however couldnt make the payment. Now I just received a call that my balance is over R900, how does the bank charge interest of over R200 in a space of 3 weeks? How else can I deal with these people *****ing my money. To my knowledge the account was closed and now I owe them? this is ridiculous