Unfair Refund Treatment

I bought 3 back to school items from Takealot with the FNB promotional code of R100 off if you spend R500. The total cost of the items I bought amounted to R673. I returned a lunch box which was of a very poor quality which had cost me R119. Now take a lot only refunded me R19. This does not make sense to me because had I bought only the two items I kept, I would have still received the R100 discount as they were above the R500 required to enjoy the discount. Takealot please refund me the full cost of that lunch box what you are doing with this transaction is *********.