Unhappy Customer

I purchased brake pads about 3 months ago at Goldwagen Southdale after I provide them with my VIN number of the vehicle. As my pads still had about 30% life, I kept the pads for about a month or so, when I took it to my mechanic to fit it, he opened the box removed the pad only to find out that it was the incorrect pad. I returned the pads to the store and was told that they could not refund me as the box was open 'duh'. They told me that they will attempt to sell it and refund me, it is now a couple of months later and I went to the store and was told that they are not able to refund me. This is totally unacceptable, they should have provided me with the correct parts in the 1st place as I provided my vin number. Secondly how was I supposed to know that the pads were incorrect without opening the box. This is a *******.