Shocking service and not receiveing paid for items

I place a large order and 2 items did not arrive in the box. The one indicated no stock but the other more expensive item indicated they sent it. This was 2 weeks ago and after phoning them and emailing them with pictures of what was in the box I have still not received the more expensive item or been refunded. The cheaper item I was given a voucher for the same value but not for the second item. I have emailed 3 times and phoned 4 times and each time it is like I am logging the complaint for the first time. Each and every time I get the same words "there is nothing on the system so I will have to check with the warehouse and then call you back" and guess what...I have as yet never been called back. Yesterday I even asked the guy if they have a script they work from because they all say the same thing and no-one knows about my issue even though, as I said, I have mailed 3 times and phoned 4 times. I have no idea how to get my item or a refund of R599??