Bid or Buy dishonest sellers on their Platform

I purchased a 9ct white and gold ring on Bid or Buy last year in June for 3500. I recenly had the ring together with my other jewelry tested for insurance purposes.

I was stunned and disappointed to learn that the ring is not gold, the tester that was used turned the band of the ring bronze. This indicated that the ring is not gold. Both the seller, goes as abargainonline and Bid or Buy have not provided resolution and further to that my ratings and payments made to the seller have been removed off my profile which is suspicious and dishonest behavior . Truly disgusted with the lack of accountability from both parties.