What to do?
Either one or all of the following:
1. Forget about it (what United is hoping for)
2. Continue pursuing it with United
3. Never fly United again
4. Complain to the DoT
5. Use social media to humiliate United.
Personally, I think it makes sense to go the humiliation route, because I'm of the view that they deliberately try to cheat people in these circumstances and that it should be substantially more expensive for them to take that route than to treat people properly.