LOST LAPTOP

Hi I am not happy with the service I received from Lewis KwaMashu Shopping Center I had a laptop that I bought from their shop after a while just stopped working I took it to their shop I was told to leave it they will get back to me once they have got the quotation the other day the lady phoned me and told me that they won't replace the laptop because it was my fault but they did the quotation I will have to pay 50% of the quotation I told them I still pay for it and it is insured and I was told to come with the affidavit explaining how the laptop stopped working I gave them the Affidavit the store manager phoned someone they both agreed to each other that I won't get the replacement I just told them that I need my nonworking laptop I'll fix it myself. The big issue now is they lost my laptop in their storeroom so I'm not getting the replacement and my nonworking laptop because they lost it. Please help