Short changed by Clicks Garden Centre

My medical scripts are with Clicks Garden Centre, I went to get them the other day and got home to find 15 pills missing (so I had paid R450 for 45 pills instead of 60). When I went back to try and sort this out I was met by their very rude and very loud manager who insisted that I was lying and that their books were perfect and that it must have been my fault. I know that the pills were missing and so all I can imagine is that someone must be taking pills out of boxes behind the counter (the pills were Ritalin!!) and so I am pulling all my scripts from Clicks and taking them somewhere else.