The store refusing to refund me for purchase made

I went to buy clothes at Fashion Express in Centurion Mall on Saturday. I took the items home and realized that i was not happy with the good i bought. I then went back to the store on Sunday to exchange the items for different sizes, only to find that the store didnt have any sizes that i wanted. I then asked Tumi the cashier to refund me the money back and she told me she cant because the till didnt have any money. She spoke to me as if she was doing me a favor. She was not even interested in listening to what i was saying to her. Instead she told to walk around the mall for 2 hours and came back at 5pm and maybe they will have the money. She was rude and unwilling to assist. In their T$C they say if you return the merchandise within 30 days in their original condition and with a slip they will refund you. <br> Is this the customer service we supposed to receive? Please assist because i want my money back. I refuse to shop in a store were the employees make me feel like they doing me a favor by selling me the goods. Please respond URGENTLY!