Crocs service sucks

Crocs had a black Friday sale and I bought 4pairs. One of the pairs didn't have the correct size but the color I wanted and the shop assistant assured me I will be able to exchange it for another color in the correct size. Now they have long stories not to exchange it. Why would I sit with a pair that I can't even use. This is the worst experience. Before visiting the store I called and they were even rude, therefore drove all the way to be treated like this. Can someone competent please help.