I had the same thing happen to me on the second tank refill 2014 rts, Had to get off with a large pair of channel lock pliers, took about a month and a half for dealer to send me a new gas cap, in the mean time the cap got harder and harder to get off with vise grips so I went to local NAPA store and matched one up, the new cap came from the dealer the next day and no problems so far needless to say I still travel with a large pair of channel lock pliers in the frunk.
Same here used large channel locks to get it off... My dealer had 3 in stock... no charge...