Waste of time

I searched for a top online which I found at promenade mall. My sister lives in Mitchell's plain so I asked her to buy the top for me on her account. She gets to the store, gets the top and I picked it from her. I realised the top was too small so I took it with the receipt to the store for my exchange for a bigger size. When I got to the till I was told they cannot assist me because I didn't have a gift receipt. The cashier never advised my sister about a gift receipt but mentioned a gift card which she didn't want because what if I didn't like the top then I would be sitting with a gift card I didn't want. The cashier and manager both full of attitude couldn't do the swop. My issue is: WHY COULDN'T THE CASHIER SPEAK UP AND ADVISED HER ON A GIFT RECEIPT? THE CASHIER ADMITTED SHE REMEMBERED MY SISTER BECAUSE SHE ASSISTED WITH THE PURCHASE! WHAT A WASTE OF MY TIME! THE FACT THAT I DROVE ALL THE WAY FROM THE NORTHERN SUBURBS FOR THIS ITEM AND HAVING MY SISTER DROP EVERYTHING TO COME AND BRING BACK HER CARD. PETROL, TIME AND EFFORT.