Aramex overcharged

I bought goods in from USA and my invoice amount was for ****.00, Aramex charged me duties and taxes etc for an invoice of $779.00. After sending them numerous emails and sending my invoice and “TRYING” to explain to them that they have overcharged me. I had to pay R5769.33 for duties, vat etc.. I have had no response from then and no one has been willing to help me get a refund for being overcharged. I haven’t even received my goods yet,