Given the transoceanic surface sector exception for an SWP originating xONEx you should be able to reissue the ticket with the sector deleted.

Your other choice is simply to discard the coupon and carry on as booked, hoping that it won;t be noticed and that if it is no one will be bothered. This is very much 'taking a chance' though and I wouldn't recomment it.

It seems to me that the best option is to keep the xONEx as is and lose the other ticket - which other than being annoying has no consequences.