Rudeness in foschini stores Richards Bay kzn

I went to foschini stores in Richards bay kzn to change a dress i bought in foschini mall of africa two weeks ago,i was told that I have worn the dress. I told them to conduct investigations i have never wore the dress hence every price tag was in the same position not removed. The lady told me they cant assist me,the dress cost like R2000. Lady was very rude telling me how can she believe that I didn’t wear the dress because other people do it,I have never been embarrassed like that in my life. The dress has never been used,it has been in my possession since the day I bought it. I paid cash for the dress it my money.not that I wanted a refund but an exchange. Kindly assist me for the dress to be changed. Thanking you Sbongile Myende