Not quite telling the truth about a refund

On 3 October I ordered two items from Zando costing R449 each. I paid R449 by EFT because I was R449 in credit with Zando. When the parcel arrived I did not like one of the items and returned it. Zando don't understand that they owe me R449. They have told me they have paid me two refunds of R224.50 totalling R449 but these alleged refunds do not appear on my credit card statement. I have sent them copies of my credit card statements showing they did not make either refund, but as far as they are concerned, the case is CLOSED. And they still owe me R449.