Sterling silver necklace broke 2 times and the silver fades

I have a American Swiss Account for the past 2 years. I bought a sterling silver neck chain at American Swiss N1 City a year and a half ago. Since I bought this silver neck chain I have had problems and had to take it back 4 times. The 1st time the chain went dull like a grey colour and was staining my skin. Every time I complain and take it back to American Swiss N1 City they just send it away to get polished and cleaned. The 2nd time it went dull again. 3rd time the whole chain broke into pieces. I took it back again american swiss n1 city send it away again to get fixed and charged me R500 when I got it back 2 weeks later it was polished so thinly the same day I received it back it broke again. I am disgusted the chain was R2400 and is suppose to be real sterling silver and not break and fade so easily. The customer service just sends it away to be repaired and I must just pay each time.