Cartier TRINITY adjust size

Hi Everyone,
I think I will need some help from You. I bought a Trinity classic ring 5 years ago and today, after doing a lot of sport, I lost quite a lot of weight. The ring is a little too big now, I would say about two sizes. Does anyone of You had already this kind of problem and if so, did Cartier did ajust the ring? Could you please tell a cost of this kind of service.
Thank you & have a nice day,

Tom