Hi, just a short question. I'm a mobile mechanic. I've done some work on a customer's car three weeks ago. When they picked the car up, they said they were very happy with the work, and loved the job. They payed all monies owed in full, and left. Now today 20/8/2014, I got an SMS from them asking for money back, for work they say i didn't do the job. The car was not running when it came to me, rusty pannals, which I repaired. I gave them a free car detail, as well. The car left here running great, but they want their money back,or they will take it further. What do I do under Australian Consumer Law? Thank you.