Business ProfileforAll Nippon Airways

I bought my familys and my ticket through United. Four total flights, only one long leg operated by ***. We were only allowed to pick the middle seats and not allowed to pick any aisle seats. We were advised by multiple *** agents that we can only change our seats 24 hours in advance before flight. They asked the front counter to try and seat my husband and I and our 2 year old son together, but thats a request based on seat availability. I tried to check in and pay for an advanced seat reservation so our family of 3 can sit together. Tried the app and website and both said if we are unable to, please call *** customer service. Called, and agent was rude, interrupting, repeating the same thing over and over again, saying that we just need to ask for seats at the counter, and theyve already sent a request in. It also said that they are unable to see the seat map anymore, but when I called a month ago, they said they cant see the map then, and for us to just wait for 24 hours before check in. The agent said it shows were all checked in, now just assign seats at the counter when we get there. Ive called multiple times for you guys to tell me nothing can be assigned until 24 hours before, now Im calling and you guys are telling me I cant do that either, just try and get seats together when you get to the counter. So Ive been mislead and misinformed this entire time? Your website and app is extremely not user friendly, its a loop that takes you in circles without flat out saying we just cant do an advanced seat reservation, even though the page itself says we can. Then I called multiple times hoping an actual person can be more useful, and weve been absolutely let down every single time.