Can search the company registered address and director and start a lawsuit against both. If you worked with the director particularly try to sue them to held them personally liable (not likely to win but the more problems you cause to them the faster they will settle). Small claims is easy (so I've heard, I never experienced it myself) but you can only sue for HK$50,000. You can do it without a lawyer but should learn some legal terms, and defend any BS mentioned in court by the defence. Failure to respond to one tidbit of information will be used against you when quantifying settlement.
You should quantify your losses as well to make it easier. Receipts or get report done by an appraiser or whatever you call those people.
Also inform the media to give bad PR to this company. I would send court docs, photos, videos and email communication to all media agency + the company + company admin/sales emails + company directors. You can also CC any companies that this company is known to work with to notify HR and MD's/C-level staff of their poor service. Make sure your photos and videos are clear and concise.