I have tried multiple times on several different devices to purchase two seat reservations from Paris to Nice and vice versa and every time i get to the point to proceed to payment it says one of the legs of this trip is no longer available even when attempting to purchase one portion! Ive had others try to purchase the same times that show as AVAILABLE on their device and keep getting the same error. So there is no way of knowing if the seat is available or not! How do I proceed?