bad customer service

I bought shoes for my children and saw that my daughter shoes are big then i went back to the store today 19-12-17 to exchange for a small size and I could not find the shoes as they sold out i asked if i could get cash back they said no because i lay byed i have to exchange ..so i took another pair to exchange i joint the line and when i get to the tills the cashier said next and i went but when i arrived i told him im exchanging he told me he is not exchanging I must go to the next till wen get to the next till the other cashier told me the same he said i must wait they taking cash and lay bye out ..i wnt to the 3rd cashier she also told me that their till doesnt exchange only one till is doing exchange ..i would let people pass me to go pay and i was standing like a stupid waiting for help and they laughed and say i can come ..all my lunch waisted at the store ..wat made me to get ****ed worse is when the guy finaly wanted to exchange and called the supervisor for authorisation and the lady stood there and foulded her hands and staring at me ..the cashier called her 3 times and she never came .i had to take my exchange a leave the store coz it was too much for me ,.my children are going visiting tomorrow and i couldnt change her shoes.. What does management teach the staff? .they have very bad atitude towards customers ..and this is not the first time they do this