Sterling silver plated

We bought a sterling silver engagement ring from sterns in centurion mall when we got engaged 29 November 2015 my fiance started wearing the ring less than 2 weeks later the silver on the resized part. The ring is stamped 925. What we want to know is how does sterling silver with a stamp fade away? What are you as a company going to do about the problem?<br> <br> <br>