Unsatisfactory treatment

<p>I bought 2 gold/diamond rings and then put them away unused (for a long time) when I opened the box again the rings had turned black and when I brought it back to Carls Jewellers they didn't care and even wanted to CHARGE me to have them polished !!!!!! Is this what gold should do ??</p> <p>not sure What I was sold originally - couldn't even see the gold stamp inside the ring ???!!!</p>