Failure to Close Account

I had student archiver account with standard bank since 2010 and I have been a loyal costomer to them for year. In February 2018, I decided to close the account and move to other service provider. I went to the branch in Festival mall, Kempton Park to close the account which was not owing even a cent at the time. I was then told that if I don't use the card for 3 months, it will automatically be closed and I went home and never use the account until today. I was convinced after that the account is closed as they stopped communicating with me on status of my account like they used to do all this years. Late last year, I decided to go open account with them again, that's when I find that I owe the bank money for bank charges as they never closed the account. They told me I should have got the letter that says the account is closed, how was I suppose to know that I should get the letter? They say I should pay the money otherwise the charges will keep on increasing.

I am asking myself this question: 1. Is it my responsibility to ask for letter to prove the account is closed? 2. How do I know that there is such letter? 3. Why did they stopped communication with me because I should have realized that the account is still opened?

4. Last year my car got financed through standard bank, why didn't they pick it up during the process of financing a car that I'm owing them? 5. When were they going to tell me that the account is owing such a big money if I never went to open account again?

I am here asking for help, I have tried all but I failed. I have been loyal and still loyal to them, but this is the thanks I'm getting for being with them for all this years?