Rude Mr price cashiers

My sister bought me a dress last week so it's small, I went to Mr Price greenstone and they didn't have the size I asked them to check and they called birch acres mall they confirmed they have the size and she asked them to keep it for me because I'm on my way. I get there and the rude cashier tells me she wasn't the one who answered the phone, she asks the other ones and they all say they don't know anything. She then tells me to go and find the dress bcoz she knows nothing. I get to the dress the and there is no size she then says she can't help and hands me my slip back to go and collect the original dress I came with she didn't even try to find the dress or atleast check for me where I can get the size she was so rude. These Cashiers really need to go for customer services training because they are clueless. I never wanted to believe when people say black Cashiers in suburbs are very helpful because whites are quick to complain but the black Cashiers in the location dont give a hoot about their fellow people it's very sad. I still have the dress and don't know where to go and check.