Disgusting and arrogant attitude after sales service

Please help, bought a watch & necklace from folli follie(menlyn) on 17/08/2019.In December the black necklace I purchased started to change color, I put it aside and didn’t wear it anymore, last month I went to the Sandton shop and I was told a manager will call me in a weeks time because she was away, this week I got a call from the lady who helped when I returned the necklace and I was told they can’t help me and I must come pick up the discolored necklace. I refuse to go pick it up because since December. I was not told the necklace was poor quality when I bought it. I was told it will stay black otherwise I wouldn’t have bought such an expensive necklace knowing that the color would change. I need help as these people are so passive and arrogant. The lady’s name who helped me is Precious.