BAD SERVICE

I bought some food from shoprite Lebowakgomo, then withdrew R500. I just took the cash and put it in my wallet. To my surprise it was R400 when I checked. I went to the shop to enquire. They checked the camera without me. They told me that they saw it on the camera that I was given R500. I asked to see the footage but they refused. Why would they refuse with the footage if is true.