Well I think calling them would be wise - I ran into an issue with an NH - SG - NH - UA chain of flights... HKG was having a typhoon and SG let me change flights - but the original one still went out without me - and then NH cancelled all downstream flights on them and on UA due to no show! I had to BUY all new tickets. Of course this was a revenue ticket - but can't see any reason not to call and get options....