Sterns poor quality ring

I bought a silver ring from the Sammy Marks pretoria branch on the 28th of July 2023,and the has discolored and changed to black. Took it back to the Soshanguve crossing branch and according to them it could be my skin or the lotion I use that discolord the ring. They put the ring in a cleaning solution and the discoloration is still there and I was given back the ring and told to go the branch I bought it from. Honestly that's pure nonsense and the staff there were rather rude not friendly and not willing to assist with my query. In less than a month I refuse to have a ring that will always discolour. So I want my full refund because I'm not happy and will not trust anything from Sterns.