Stinky attitude and service

Bad service I got from a lady at Mr price Rosettenville Junction. The lady was just not willing to help at all. And I feel like she was looking down on me not knowing who she is dealing with. I bought a pair of sandals from the Glen shopping mall Mr Price on the 24 Dec. Mistakenly took a size 9 intead of 6. I decided to take it bake on the 30 Dec to the nearest which is the one at the junction. The lady there first told me the shoes are dirty they were used, she then said she can not refund me if there is no slip which is understandable. She went on saying I must produce emailed slip which you could tell by her facial expression she thinks I know nothing about emails. I said I will take something for exchange hance I didnt have slip. She checked the price if its still the same when punched on her retail till. It was ok. I do not know what she did but when I came back with the item for exchange she said the shoe is on promotion which was not there five minutes ago. So now I need proof that I did not buy it on promo. It was a slender dark lady with condraws. I think she is a supervisor there