I am booking a trip to Shanghai later this year, would like to travel in the new Y+ seats SIN-PVG, however the mixed class booking option no longer shows up when I search for flights. Y+ is definitely available on the SIN-PVG legs, so what would be the best way of completing this booking - do the whole thing via SQ call centre, or book the Y fare online, then call up to try and upgrade? I've never had to call SQ before, are they generally pretty competent?