Defaults on new car

My wife purchased a new car at Toyota Arcadia and collected the car on 2015/10/22. I realized the following defaults on the car when driving. a) The car shatters when driving over speed humps b) The gear shifting is not smoothly c) The car drives very hard. The Service manager test drive the car and agreed. He deflated all four tires from 2.20 to 1.80 but the hardness and defaults is still there . The car was booked in twice but the defaults are all still there. After working on the car the first time I saw the rear bumper is loose. Before working on the car the second time I ask Toyota to tightened the rear bumper and check all defaults. After the second time collecting the car all the defaults are still there. The rear bumper is still loose and 1 damage mag . On several occasions I raised a complaint at Toyota SA as well requesting a new car. I was informed by Toyota SA that it cannot be replaced with a new car and must be fixed till it's fixed. Toyota wants to work on this car for the third time now but me and my wife is not satisfied at all with any service from Toyota. In my opinion how can you fix a new car which was not suppose to have defaults. Please help in this regard.