Thanks I didn't see them on twitter but will check again. Yes it says you need to pay for seats which is why I was surprised to see a seat automatically assigned however when I did a mock booking it shows the seat available. I spoke to United and they can't do anything but refer me to Edelweiss. They gave me another PNR which works for Swiss but not Edelweiss however that shows assigned seats but unable to change. The flight is in Sept so enough time to get this sorted out. I suppose I could fill out that form for seats as I would prefer the Eco Max seats for the extra legroom for long flight (LAS-ZRH)