Bad service at mthatha couch works

My mother took her car to Mthatha couch works as recommended by her insurance. Everything seemed to be going well as the repairs took just a week. But when she went to fetch the car she almost went blind when she saw what was done to her car. They used the wrong color paint and they fitted the wrong bumper. My mom doesn't know much about cars but if she was able to spot these then Mthatha couch works must have really did a ****ty job. To make matters worse they maintained it was the right color and correct bumper. Only when she requested the invoice showing the they bought the bumper from OEM did they tell the truth that her bumper was still in transit. How do you work with such people? I demand an explanation.