Irate client

I sent my son to buy samp at spar he mistakenly bought beans, now I came to return it with the receipt beans are still on the original pack. The supervisor that attended me said that I cannot return these beans that the new rule, I asked did they tell the person that I sent that he must be sure because he cannot return what he bought she said no. I made example that at any store when you buy something that you cannot return, you make sure that the client is aware of that. I ask to speak to the manager he came after 25 minutes just say he cannot change it with big attittude that's it his name is Simphiwe Khumalo.