BAD SERVICE EVER. Dishonesty

I took my injectors there for testing, they told me the 4 injectors are faulty. and i asked for quotation for repair of which i was never given, just when i go there to collect the injectors and the report, i was told that they've already started fixing them and they will cost me R17 000, firstly i have never given them the right to fix them and i told them i wont be able to pay such amount, its like buying new injectors. they said they can reduce the price for me and there was no way I'm going to get them, well new quote was R14 000 which i paid after they've promised to give me the 6 months warranty documents. i collect the injectors with my mechanic and as they promised i was not given the warranty but the lady by the name of Pinky assured me that i will be assisted should they give me problems. right after putting the injectors on, my vehicle was still smoking and i went there within 2 days. All they could do was questioning if i did the service on the vehicle and if i did service the diesel pump, because this was getting too much, and they didn't want to help me with the injectors that they fixed incorrectly, i asked for a diagnostic before removing anything on my vehicle, i left the vehicle with them for diagnostic which was R700, to my surprise when i go there to collect the vehicle i was told that they removed the injectors from the vehicle to fix them because my mechanic didn't fit them correctly, the following day i was told that they changed the parts on the injectors and i got a new quotation and still the car was even worse this time around, didn't even have power and the smoke was worse. I have never agreed that they fix the vehicle but they did without my concern, they never gave me the Diagnostic report and i was over charged again. they are so dishonest and charging people over where else they cant fix the problem and always looking onto something to blame. i am going to escalate this matter until they reimburse me accordingly. Bad service i have ever received. you take advantage of people.