Standard bank de*****ing blacks again like fnb

I took an overdraft of R21000 from standard Bank and recently decided to close it and from November until February I deposited 4500 and just yesterday I got a call from some gentleman saying I am owing standard bank 500 on my overdraft and I asked him how is that possible since I had deposit 4500 since November 2018 and I have not touched that money since, where is the money going and he said interest and I asked him how can I pay R4500 on a R21000 overdraft in 4 months and his response was he does not know and he will come back to me.....I am still waiting **********