Tarnishing silver nameplate necklace

I ordered a silver nameplate necklace from American Swiss Pavillion. After receiving it and wearing it for about two months, I noticed that it was losing colour. I took it back to the store only for the manager to tell me that unfortunately that's what happens in Durban because of the humidity. She told me that I would need to pay for it to be sent away to be dipped. This is after spending R800. I was willing to spend that amount on a silver chain as I wanted something I could wear daily.