not everything that shines is GOLD!!!!!

I BOUGHT A 9CT GOLD PINKY ONYX RING FROM ELDORADO JEWELLERS ON THE 24/12/14, AS A GIFT.THIS RING HAS SINCE BEEN USED 2ce.LAST WEEKEND,WE NOTICED THAT THE RING HAD CHANGED COLOUR.NOW WHAT 9CT GOLD CHANGES COLOUR IN 2 MNTHS?I CALLED ELDORADO JEWELLERS ON 26/02/15 FROM MY WORK PHONE WHICH IS RECORDED,2 TELL THEM.THEY TOLD ME 2 COME IN TO SHOW THEM,WHICH I DID.WHEN ARRIVING TO THE STORE,THE PERSON WHO HAD SOLD ME THE RING (RAVIN) WAS THERE AND TOOK A LOOK AT THE RING. A LADY CAME TO SEE THERAFTER AND ASKED ME IF IT WAS IN THE BOX THEY GAVE ME BECAUSE THE BOX THEY PROVIDE HAS A CHEMICAL IN IT THAT POSSIBLY CAUSED THE COLOUR CHANGE,THIS I WOULD THINK 2 BE AN EXCUSE AND ANYWAY IT WAS NOT IN THAT SPECIFIC BOX.THEY KEPT THE RING AND SAID THEY WOULD SEND IT BACK 2 THE SUPPLIER & WOULD GET BACK TO ME IN A WEEKS TIME.THEY CALLED ME 27/02/2014 & SAID THEY ENDED UP SENDING THE RING TO AN INDEPENDANT COMPANY TO TEST IF IT WAS 9CT AND IT CAME BACK 100% & THEY WILL NOT REFUND ME OR EXCHANGE.I TOLD THEM THAT I CANT BELIEVE THAT THEY SENT THAT RING BECAUSE THEY COULD HAVE SENT A REAL 9CT RING,THERE IS NO BARCODE TO PROVE.NOW I CANT WASTE MORE MONEY TO TEST IT FOR MYSELF AND JUST WANT MY MONEY BACK!