Online purchasing

I made a purchase today online for a hisense 95l deep freezer. Paid online and all, then here i see that the defy deep freezer 195l is also on special. So i called in to hifi corp immediately wanting to know if i can swop the two and pay in the difference. This happened within not even an hour, so the consultant tell me that is impossible. The order is already set aside, keep in mind its still in the warehouse. He also tells me if i really want the defy freezer i must purchase it. He tells me my best bet is to request a refund of which i would wait 7 to 14 days for my money. So now he wants me to request a refund of which i will not receive the money now and in the mean time make another purchase because this deep freezer is on promotion. Like i have such money laying around. Even if im getting the money back for me to make another payment is ridiculous and its festive. My budget does not allow it. And why should something so simple be so complicated. All i want is for the swop to happen and i pay in the difference. Its like a in-store exchange. I am really upset by this. If i must wait for my refund the promotion price may be over or the price will be up or even no stock.