I have a Diamonique ring I bought about 20 years ago. When the main stone clouded--this was about five years ago--I called customer service and they said they would be able to dig up my old order from microfilm storage. I had to make a request in writing, tell them approximately the year of the order, and my member number.
I never followed through. The reason is that CS told me that they would not repair the ring or replace the cloudy stone, but rather send me as close a substitute as they could find in their current inventory of DMZ rings. Wasn't interested in that. My old DMZ ring is a substantial ring of solid gold. I'm sure nothing they have comes even close.
I've considered taking the ring to a jeweler to have the CZ replaced, or maybe replaced with a gemstone.