Brown's Diamond Store - still going strong despite almost unanimous bad reviews

I am at my wit's end with Brown's Diamond Store. They stole links from my gold necklace while it was being repaired, and then refused to do anything about it. As a sop to me, they offered to buy the necklace back for the value of the gold only - which is a fraction of the actual value of the unwearable necklace. They ignored all requests from the Consumer Council for an explanation. They refused to co-operate with the investigator. They have received nothing but bad reviews, similar to mine - dishonesty, sharp practices, outright *****. Yet they continue to operate, with glamorous shopfronts, deceiving people with outward gloss. What can you do about a company that simply refuses to account to their unhappy customers?