Last year, I used to bring a lens brand xxx to the customer service to change for new set after discover faulty (front focus) within 3 days.
I did convince the technician for 1 hour after he tested the lens and gave conclusion that it's normal (while in the end, it's not).

Yesterday i visit a local reputable shop yyy and saw him as a sales men.
I think he didn't recognize me .
Wonder will he recommend brand xxx during sales haha