H&M Westgate is trash, poor customer service

H&M westgate shopping mall has very poor service I bought a Jean that’s on sale yesterday for R200 picked a size smaller to top it off I asked the cashier if I’m able to change the size if it doesn’t fit she agreed today I went to do an exchange they telling me I can’t exchange the size with the same price I need to pay the difference because the tag shows the Jean for new season yet they still have sale going on in store that was so pathetic and not even helpful they don’t care about customers and their consultants are poorly trained