Originally Posted by
yycworldtraveler
Call NH and ask them to assign your seat or ask them for your NH PNR# and then choose your own seat on their website.
If it is a codeshare flight NH can do nothing about it. It is about UA only purchase certain row of seats in C and Y, you cannot change your seat til checkin at the airport.
If it is NH number, then it is fine. I suspect OP is in the first scenario.