Very bad customer service, no accountability at all

So i bought sneakers on the Cyber Monday sale with extra 15%, when i was checking out i entered the voucher code for the extra 15% CYBER15 but to my surprise, the next page was the one with order confirmation and the extra discount was not deducted. I then send them an email advising that the code was not deducted and an automatic reply came back saying customer service will call me, which was at 15:10. Since i have not been called i decided to call today at 13:10 and the lady i spoke to advise me that my order has been shipped and there is nothing she can do, if i don't want the order anymore i should just return it. At this moment i am shaking with annoyance and the level of not caring, i could hear from her voice that she thinks i making my problems her problems. Very bad customer service.