Prosource Monroeville Prosource Pittsburgh Prosource Prosource Pgh Prosource Monroeville knowingly sold me faulty product and refuses to take it back Pittsburgh Pa

Prosource sold me a stone tile/backsplash product that MUST be cut wet.  However, it contains a water soluble glue which makes this impossible as the stone falls off the mesh backing when it gets wet.  I was NOT made aware of this when I purchased it and Prosource denied knowing the issue even existed until my last phone call with Ed the showroom manager, who was dumb enough to admit they knew it was an issue.  I spent countless hours calling and emailing both the manufacturer and Prosource attempting to learn a way to be able to install the product as my wife and I both really like it.  I even purchased 3 additional new diamond blades in an attempt to cut it.  The final answer the manufacturer said to do would cost more than the product itself did, take countless hours of work, be nearly impossible to do correctly and completely make the product un returnable.  Prosource refuses to take back the product except under unreasonable circumstances, only taking back non cut and non broken sheets, a 25% restocking fee AND my paying the freight back to the manufacturer.  The manufacturers rep admitted to me on multiple occasions that the situation was ridiculous but still I cannot get an acceptable resolution.