Thats why you need to introduce some competition. This will make them realise they have to provide customer service. On the other hand, I fully agree with you that many ppl in Hong Kong know nothing about cars, they care more about 4-leg animal, and make unreasonable demand. My wife once complainted to Wilamn about the "short life" of the brake disc he fixed, after the car had done over 20k. I suggest you consider organising some half day promotion sessions to new Reno buyers/potential buyers. What I have in mind is a half day party (Sunday afternoon) in your workshop, about 30 to 40 families will be entertained, a number of reno will be made available for test drive, some keen reno users will be invited to share their experience, your chief mechanic will give talk on technical stuff, how to modify reno...etc. Such activity wont cost too much, some snack and drink, maybe. Worth trying.
Tony