Firstly, looking for "service" among our American legacy carriers will lead only to frustration. They don't give a rat's patootie about customer satisfaction.
However, I suspect the mistake was not learning to play the game. All of the US carriers that I know of, (except Southwest, which has its own ways) provide advanced seat selection. It's years since I showed up at the airport without an assigned seat. However, the seat selection may not open up at the time you book. You have to go back later and recheck. Personally, if I am unable to confirm my seat by 30 days before the flight, I am on the phone to the oxymoronic "customer service" line -- in most cases the rep will be able to confirm your seat.