Hello, I'm in need of urgent Australian consumer law help or advice... My 2005 Nissan Navara d22 developed a misfire/loss of power problem. I took the car to a local mechanic to find out what the problem was he diagnosed the problem to be a faulty EGR valve and that it would cost me around around $600 for the genuine part and another $200 to fit it. I booked the vehicle in a week or so later to have it fixed. He rang me to collect the car and said the problem was fixed after picking up the vehicle it was clear that the problem was not fixed went back in to rebook the car so he could have another look at it he then diagnosed the car to have a faulty injector pump rough price was over $5000 as the problem was diagnosed wrong the first time. I asked for a full refund that he gave to me but then slapped me with another bill $870 just for him to diagnose the problem for the second time but problem still not fixed i then done some research and found that it was not the injector pump that was at fault and that was actually a $60 electronic switch on the gear box went back in again to speak with the mechanic about it and told him think i have found the problem he ended up abusing me in the middle of his shop and almost become physical after coming out with a crow bar.. i then had a written report done on the vehicle at the local nissan dealership and was proven that it was infact the $60 gearbox switch not a injector pump with proof i then asked for a full refund for the $870 that he charged me to diagnose the problem that was proven to be wrong he has refused to refund me the money saying that a lot of time was spent on diagnosing it even tho it was incorrect diagnose. Then after not hearing back from him for 3 weeks, I received a call from him saying that I have to give him back the EGR valve because he refunded me the money for it (money that i never touched because it went on to the other bill) and if I don't comply he will put me in to debt collectors for the $600.