Bad customer service

I bought a shirt on Saturday as a gift to someone unfortunately that person didn't like the gift I went to sportscene in dobsonville they said they can't assist me coz I had lost my slip so I need to go back to the store I bought it from.. Even though I had the transaction on my bank statement as proof they still refused. I called their customer service center and they told me that the store takes their own decision so they can't help me. Now I'm stuck with a t shirt that I can't change of 400!!!!!