We are a car dealership and we buy $1000's in auto...

We are a car dealership and we buy $1000's in auto parts every month usually from the local parts houses. we are in a big city so there are plenty to choose from so they can deliver same day. We purchased a catalytic converter from rock auto and this being our first purchase from them. The part was cheaper and we could afford to wait a few days to get the part. We figured this might be worth while to start buying parts from them. the part arrived. We had out ASE Certified mechanic attempt to install it. the flange was miss shaped and hit against the oil pan. Ok it was worth a try. I went on rockautos website to file for the return. I answered a few question. I was told that I would hear back in a few days.In the mean time I could no longer wait for a part. I ordered it from a local vendor and had it same day. I had not heard anything back from rock auto so I logged in today. It now says that my part is non returnable. WTH!!! I get that we installed it. we knew right away it didn"t work. they should take it back!!! there is no customer service to talk to about this. never again will I do business with this company