Catalytic Converter Replacement

I went into this shop to shop replaced my catalytic converter as the check engine light came on. Has the diagnostic done in that shop that read one code, which translated to the cat converter needing replacement. Well they replaced it, but when I saw them bringing my car back to the floor, the employees were pushing my car. I get to my car and three notifications are lit on the dashboard including the "check engine light." Now my car doesn't drive past 5 mph. Well I took my car to the dealership and apparently the Fast Traffic Mufflers employee somehow managed to reset the car's computer, leaving me $1000 in the hole. The deny any wrong doing and refuse to assist with repairs. I will be seeing them in court for reimbursement. Please save your time and money in taking your car here.