Wedding bands

My husband and i bought our wedding bands at American Swiss December 2014 for our wedding which was in September 2015, 2 months before the wedding my mother decided to double check everything that we had so that we can see what still need to be bought, when she opened the wedding bands boxes the bands were black and we took them back to the store and they cleaned them for us and 2days later we collected them however 2 weeks later we notice that the rings were black again an we took them back to the store where they were cleaned again and we where told to rather collect them the day before the wedding which we did. 1 week after the wedding i notice my ring going black again and i returned the rings and i asked for a refund which was given and they talked us into changing instead of refunding and we agreed. My husbands ring looks 20 years old now and we only been married for 5 months, please assist very unhappy.