Infinity disappointed 😞

Very dissipionted in American swiss.....my husband bought me a Silver and a Gold infinity chain in October last year for my bday. So the chain an pendant on the silver one has turned black. Took it into the Festival Mall shop and was told they can book it in to have it cleaned but there is going to be a charge. How do you tell customers you sell something that is Silver but it's not. Very very frustrated right now.