I use to work for them. You have not made an actual purchase until they had you the product. Therefore you have the right to demand your money back. 

If they give you crap ask for there customer service number and the name of their District Manager, Store Manager, person helping you and their store #. This stuff is usually all on your recipt that you have with your pre-order. But asking for it should scare them to cough up your money.

Again i say you have not purchased a product therefore they have to refund it to you and they know it. DO NOT TAKE STORE CREDIT or you will make things much harder on yourself.