Important to find someone reputable. My husband gave me a double set of Yoneda pearls for my 21st - (31 years ago). I had them re-strung twice - the second time I had them re-strung was in Auckland at Michael Hill Jewellers in Lyn Mall. When they were returned, they seemed extremely white, when I asked why they were so white, the jeweller told me they had cleaned them as they were not meant to be the colour they were when I took them in. They broke again 5 years later and I didn't bother taking them in again to get fixed. I left them in a plastic bag in a jewellery box under my bed. I recently pulled them out and they are peeling very badly. Very interesting though the pearl in the clasp has not done the same thing.