Worst Customer Service

I settled my loan account in full with Direct Axis on the 22nd of October. The final settlement amount provided by their consultant stated that my balance was R18,300.00, which I paid. My correct balance was R13,800.00. I made a full payment of R18,300.00, and now they are refusing to refund the extra R4,300.00. I have emailed and called them, but they continue to ignore my communications. I even attached the transaction record and the paid-up letter they sent me, confirming that the loan has been settled.