Firestone Complete Auto Care

I brought my car in for exhaust and muffler work, paid $650 and the car was not repaired properly! My exhaust still sounds the same (loud noise) I have contacted them for over 3-4 weeks but no response! I need my vehicle fixed, your service is poor and customer asst really not helpful. This part was special order but I was not informed it was discontinued 2 weeks later! Firestone located in Rochester NY Dewey Ave. I need some type of resolution or compensation! Please reply