Luxity painful and ******* experience

I found these guys on the internet and they buy and sell luxury goods on consignment. I sent them a pair of Christian Loubotin's luxury sneakers *** on 09 January to their Melrose Arch shop in Johannesburg. The sneakers were subsequently advertised as sold by the 14th of January. When I have sent them emails, they insist the sneakers have not been sold, despite being marked as sold on their website, a screen shot of which I have. They keep referring me to their online client dashboard which only acknowledges that the sneakers were received and listed. The sneakers were sold for R16 000, half of which is due to me according to the agreement we have. I feel like these people are being dishonest in hiding the fact that the sneakers were sold. The emails between myself and them show how impatient they are with my questions as I have become a nuisance. The goods that they have in their possession are very expensive and no one just gives away R8 000 and forget about it. It has been most painful to deal with these people.