Sorry to butt in but actually your agency is the one that isn't getting information, they will do everything possible to get you online as soon as possible, the wheels of progress turn very slowly at the airline, it is run by the government here and decisions can be very bogged down. Even if you were to contact one of the fleet managers in Vietnam, they may not be able to give you any answer, keep in close contact with your agency consultant!
Good luck, D.L.