Broken window pane

This morning windows,doors were delivered to my house by Build It Amalinda,EL, my mother signed the delivery note without checking the goods as the delivery guy informed her that he was rushing to KWT for his other deliveries. The builder arrrived to install the windows ,only to find out that on one of the windows ,there is a window pane that is broken. I immediately contacted the store informing them of this,only to be told there is nothing they can do about it because the delivery note has been signed. I explained that their driver was in a hurry,so the goods could not be checked. So after all the money I have spent on this store this is the thank you I get? This stores service lives a lot to be desired,and treating loyal customers like this is not good for any business I need this matter attended to asap,as I cannot every other week have an issue with the same store.