Bad quality

Purchased Engagement ring for the value of R15000. In October then resized it three days after. The after wearing it for 4months it change color and the metal broke for the amount I spend on the ring it's so bad that I have to experience all this to make it worse some guy at the store wanted to imply that I'm touching chemical with it but I don't even touch anything in my house, I think the store sell **** things for customer when I spend that kind of money on a ring I'm expecting the best quality not what I got from the store .