Deducting interest on the account that is settled

I had a term loan with them, which was paid on the 1st July, I even paid more. I wend to East rand branch to close the account to get settlement letter and they said I should call their loan department. I did and told them I want a settlement letter and they said I need to go to the branch. Who is the fool in this scenario if they don't know where should I find the settlement letter. Today they charge me interest on the account that is settled. I want my money back today not in 48hours R317.13 to be exact, they are not dealing with someone who did maths at school only how do you charge interest on the account that has a positive value. They are ***** to deduct on the 12th July, I am really having problems with Standard bank recently. They should refund my money or Nedbank and FNB is waiting for my money