Incorrect Refund

I bought 3 items from Spree. One of them had a defect I therefore returned them back. In their return form they stipulate that the return is free for 30 days and do not mention anything about submitting a receipt for the postage. They simply state that you will be refunded for postage in a similar manner that they delivered your items to you. My dress cost R899 I have proof but not they are telling me I paid R860.1 for my dress. And the other items are capture incorrectly too. They said they will get back to me with no time lines.