Botched repair

I had an accident mid May 2024: It was repaired and collected by me mid July. The delays were expected- not a problem. The vehicle appeared to be in order. December 2024-Jan 2025 during the first long trip, I discovered that some *****s had been left out of the fender liner that they replaced in July. The loose liner came into contact with the wheel and destroyed itself. I took it in to Farber Coachworks Montague Gardens on 6 Jan 2025 and the substandard repair and subsequent damage was inspected by the manager, who promised to call me the next day. This call never happened. I called them on 15 Jan, asking to speak to said manager. I was told that he was unavailable and that he would call me back soon. This never happened. I called them again early on 16 Jan: I spoke to the person who was my point of contact at the time of the repair. I asked again for a resolution. There seems to be a culture of avoidance and evasion of any substandard repair that they do...