Terrible customer service defective shoes

I purchased a pair of shoes that was on special. When I got home and walked with it a while the zip came apart and jammed. I took it back the next morning. They did not have another black pair so I took different colour. When I got to customer care they told me I had to pay full price for the other pair cause it is not on special although it was the same make and style just a different colour. I told the manager that it is not my fault they did not have my size in the black or that the shoe is defective. She said they will phone the other branches. None of the other branches had my size and I ended up paying full amount for a shoe that was on special because they sold defective items. I as customer am inconvenienced with no consideration. Terrible customer service.