Standard Bank charging me for an account haven't used for 3years

I was banking with standard bank for several years until I realized that I was being charged a lot and as you know one need to save as much as you can. I remember 2018 I went to a branch in menlyn mall to close my account and I was told to close it I need to pay R300something then I asked the consultant for what and she said for interest and I asked which interests but she couldn't even explain it. This week I decided that I want to open the flexi account and boom my old account still active and its on negating R3900 and when I check transaction history it's for monthly fees and overdraft fee that I don't even remember activating in my old account. How do they charge me monthly fee for a account haven't used for over 3years? Doesn't a account supposed to go on dormant once not used over 12months? This is really unacceptable I mean which service did they deliver to me for the past 3years not using their account?