Not broken, no refund!

I went to Cell C Cape Gate to upgrade my contract with them. Got there and the sales assistant helped me through the process. During this, I decided to purchase a Body Glove case for my new phone. When the deal was concluded, I walked out of the store and decided that I didn't want the Body Glove case anymore. I walked back into the store ****erally not even 5 minutes after my purchase) to ask for a refund and the MANAGER told the sales assistant that she cannot give me a refund because I had to prove that there was something wrong with the case! They cannot process the return of an item if there is nothing wrong with it, which is total nonsense! I never opened the package and yes, there was nothing wrong with it, but surely I have at least 7 days to return an item if I don't want it. Would love some explanation on this, but doubt that I will get any! Completely disgusted!