Originally Posted by
PTahCha
Your travel agent should be able to change the seat assignment for your. Or call UA.
And you should be able to check into your UA flight once you are in flight, or once you land in DEN.
True, though I much prefer to self service through the app: much more convenient. In the end I was able to check in on UA once I boarded the WN flight. It's just a lesson to me to not book this kind of trip as a single reservation in the future. Thanks all for your advice.