poor product

I purchased my wife's wedding ring at the Brooklyn Browns store in October 2014 for about R40 000 cash. However in November 2015 the diamond just fell out of the ring. My wife had worn the ring interchangeably with her engagement ring. We reported this to Browns who provided us with a quote to replace the diamond for just more than R50 000 as we did not service the ring as outlined in the fine print of the purchase agreement. But why must a ring be serviced? Jewellers we approached all confirmed that the service was more to keep the white gold clean than to sevice the diamond. I am therefore of the opinion that Browns sold us a poor quality and defective product for which they don't want to take any responsibility.