My sympathy. Yes, you should send an email to the HQ.
Don't think you should deserve it just because it's not an expensive cable. It's just bad service.
Years ago I bought an entry-level transparent HDMI in London at a similar price as your VDH. For some reasons it caused 雪花 when playing DVD. The dealer just returned a new one to me WITHOUT any hesitation. They did not even play the cable to see if I was telling the truth.
Consumers in HK are just getting too much bad service (and high price).