Refund my Money please

On August I paid my last installment for my vehicle which I was financed by nedbank, i asked how much money must i pay for balloon payment they told me it's gonna be R 66720,10 then we agreed on the 5 of October i paid the money to nedbank mfc account, on the 1 of Dec they deducted money from my account R4200 I was so surprised I then call on the following day i spoke to someone who said they didn't close the account she will send a request then they will refund my money but they didn't,today I called again i spoke with Lerato she was telling me stories then she transferred the phone to someone I spoke to her she was trying to explain to if they will refund me only R400, She said I was refinanced then I explain to her that I didn't take that offer and the reason for me not to take the offer it's because I said will pay the full amount I won't be able to pay for 18months and she said then that was a mistake and I asked who fault was that she couldn't answer I told her I was once financed by Wesbank and I believe they were supposed to contact me 2months before the end of the contract