Pathetic after-service/Response

I recently purchased a Mazda 3 from the N1 city branch and i have been having endless issues with their complete disregard for issues raised by us. <br> <br> After driving the car for one weekend, we returned the vehicle as the car was jerking in the top gears. After 1 week, we were told that tests were done and the matter was resolved as the catalytic converter was faulty. We returned the vehicle once more as the converter wasn't an original part (knock off) and then waited another month for the car to return. The other issues highlighted was the expired car licence, the service book and humming sound coming from the dashboard. In their defense, the converter was resolved as well as the car licence and the humming sound. The main issue I have is that I am being completely ignored as the e-mail/letter received from Craig Sevenich on the 25 August 2015 confirmed that the new book was ordered and they were busy with Mazda SA and the previous customer to get the book stamped. I sent Craig Sevenich and Gareth Otoole a follow up e-mail regarding the Service book on the 02 October 2015 and haven't had a response from either. What do i do next?<br>