Builders Warehouse Online Store Payment Problems!

Yesterday I placed an order online for a Weber Kettle braai and a DeWalt Cordless Drill. After several attempts to place the order through the online store (it kept giving errors when trying to enter the voucher codes Builders gave me, and then the subtotals were incorrect, etc.), I finally placed the order and made payment using Zapper. Zapper confirmed the payment was successful and the amount is also reflecting on my credit card. However, the website said that the order was unsuccessful and that payment wasn't received and it therefore expired. I phoned the call centre just to have them tell me the same and that they "cannot refund any amount that wasn't received". But the amount is reflecting on my statements! Now it is a waiting game as the "manager" at the call centre "is looking into the issue". I sent them all the proof of the payment - even from Zapper's support confirming payment. I dont want a refund, I just want the items I ordered. Why is this such a mission!