Shabby workmanship

Finn Auto Repairs replaced the brake booster on my bakkie for an incredible R6000 using a used part with no guarantee except for the reporting of a fault within 2 days. A week later it was raining and the one windscreen wiper blade was not working. On returning the vehicle outside of the 2 days I was told the arm needed to be replaced without even opening the bonnet. On opening up the area where the windscreen motor is located I found the motor had not been mounted and sure the arm had been broken.