Incorrect tariffs indicated on invoice on email and invoice on line

<p> I purchased goods from India to the value of R1684(including their shiiping charges) I was contacted by Carmen from DHL on 7 September and she requested that I send her an invoice. I wa billed for R520.15 for customs. They have subsequently changed the amounts to R1074. The figures are different. When I went in to pay online the amount on the invoice is R520.15. Why are ther such discrepancies</p>