In future, you may want to look at Main Cabin. It does give you an assigned seat for free, plus --as of now anyway--you can cancel and get a travel credit back. Look at the options all the way down the screen to see whether that applies to the fare you are booking or not. We did that for our trip in June and got $57 back PP. It only works of course if you will use the travel credit, but I think you have up to a year to use it.