Buy 1 get 1 free refunds

In December you had a 'buy 1 get 1 free' on sale items promotion at Fourways. I bought a dress for my sister and shoes for my child. My sister did not like the design of the dress. I decided to take it back. I asked to have at least half of my money back. The guy refused on the spot. I was told I'll have to go back and get the shoes I bought together with the dress. I explained that my child loved the shoes and she wears them. I was told I have to go back and get them irrespective because I got them for free. I asked to buy something of the similar value which is on sale. The guy refused and told me the promotion ended in December. I asked a simple question "what should I do with the dress?" I was told I can refund it and get nothing back. I just want to know if that's how you do business