Different shoes in box recieved from online purchase

I purchased a pair of shoes online from sportscene and I picked up my shoes today. When I opened them 1 shoe was the one I ordered and the other different. The staff at the store could not help me as they said because it was ordered online they can't do much. They tried calling the online department but they were closed as it is a Sunday. This is really pathetic and poor service from sportscene. How can they send a customer the wrong order. Aren't there suppose to be people checking the items before being dispatched? And since I purchased online the store cannot give me the same shoe as for some reason they are not linked. This does not even make sense, it is the same store. I definitely don't advise anyone to buy online especially items that are on sale as they offer pathetic customer support