We had something happen to us at check-in with an employee that the interactions were so awful, that it led us to cancel our flights, and walk up to another airline and book the first flight out with them.

I just filed a documented complaint through Uniteds complaint system, and the only other option is writing a letter. I'm afraid they wont give it the seriousness it deserves, when they respond. Are there any other lines to complain, up the chain?