Unsatisfactory response

On the 03 April 2015 I bought a dress at Jet store Vaal Mall branch, because I arrived there just before the store closed I did not try the dress on.... I took it from the rail and paid for it. When I got home I fitted it and realized that the length was short as it went up when I moved. Today I tried to return it , as I could not find anything suitable. The cashier at Vaal Walk Branch told me that he won't be able to give me my money back, because I did not buy the dress at their branch. Instead they will give me a gift card. I asked him why the gift card because I paid in cash for that dress?? He then told me if I want my cash I have to return to the shop where I bought the dress... I'm so unhappy with the service really. Jet store belongs to one company which is Edcon. Why do I have to return the merchandise to the store where I bought the dress? When they have branches all over??? I need a response.