False advertising

I bought a pair of Vans sneakers for my son at Totalsports Vaal mall branch last year on the 28th of November 2019 and asked the lady that helped me will it be possible for me to exchange if not get a refund within allocated time cause I'm not sure of the size and the lady said no problem as long as I still have a receipt .Today I went to Vanderbijlpark branch to get a refund because the sneaker is too small for my son he wore them on the 1st Sunday and he didn't even went outside because the sneaker is too small then I decided to pack them in the box and return it to the nearest branch which is Vanderbijlpark. I got the rude lady telling me they can't refund me my money back and she even said the sneaker is clean I then explained to her the whole situation her name is Thembi I even I asked her about the 6months refund policy man I got a lecture of my life I will never buy anything from Totalsports now I'm stuck with a small sneaker my money went down the drain.