Refusal to return item

I went to buy clothes anumber of clothes for my two children One who is 3 and the other who is 4 at jet Fourways on 9 October 2015. The lady that served me was nosipho who was rude and no customer service at all and I even told her that your attitude is not nice at all for someone in the customer service dept. no apology. When I got home I asked my toddlers to try out the clothes and we noticed that the tshirts were quite small. My kids took them off immediately and we put them pack in the plastic bag and the next day on 10 October I went back to jet Fourways and asked to exchange the clothes for bigger sizes . nosipho was there again today and she was looking at the clothes and said to my husband and I ' this tshirt is dirty. I asked her where it was dirty as I hadn't noticed anything dirty about it as my 4 year old did not wear it for long. She then shows me and I said to her this is how I got it and my kid didn't dirty it. She then called Treasure the manager and he came with an attitude and she showed him the spot she said was dirty and I explained to him that I got it like this and that my kid didn't dirty it. He was rude and arrogant and refused the exchange . I'm livid !