Glad to hear this for you. When I bought my JUC ring in Germany (a JUC with pavé at the nail head and point), I was very clearly told by the SA that I COULD re-size it up or down (I even had a witness!). When I went back to have it taken down a size a few months later, the SM said they do NOT resize. Of course, the SA that told me that had left Cartier.
Cartier did put some extra metal into the band of the ring, so it is resized in a way. It fits great now and does not spin. I was at Cartier today in the US and the SA seemed pretty surprised that they did add the metal to the band. Hopefully you will have an easier time resizing up.