Bad service Riadi auto

I took my vehicle to Riadi auto repair because my vehicle was cranking not starting. He diagnosed it and told me that it is the injectors and I need to buy all 4 injectors. Then I got the second hand injectors in working conditions. When I was supposed to fetch the vehicle he told me the turbo is broken and charged me R9000. Paid him in installments while the car was at his workshop. When I fetched my car it had a engen knock. He told me that my engine is damaged because of the second hand injectors. The guy messed up my car.