R3,000 overcharge for dollar payment?

My credit card was unused. Not wanting to have credit, I prepaid money into ABSA credit card to pay for a purchase online. <br> <br> I checked the exchange rate, transferred MORE money than necessary and paid online on Friday 28 August 2015. On Monday, 31 August 2015 I checked credit card balance and it showed the amount pending to be cleared.<br> <br> On Friday, 4 September I noticed that the amount had been changed by ABSA to be R3,000 more. Explain the exorbitant overcharge and refund me my money.