I've found NWA pretty good to work with when their schedule changes. Do they have another flight on that day that will work better for you? If so, have you tried calling them? Just say the change isn't going to work for you and ask if they could put you on the flight that will work better. I've done this successfully several times. For us what usually happens is that the non-stop flight I booked turns into a 1 stop. Don't like that, so I always call and get changed (for no charge) to a non-stop that leaves at a different time.
If there isn't another option that will work for you, you might be able to get a refund. If you have to pay more to re book on another airline, though, that isn't a very good option, IMHO. I hope you can find another NWA flight that will work.
For future reference, here's a link to OneTravel's info on Rule 240:
OneTravel.com
Click on the link for "Rules of the Air" after you get to the site. The link should be on the left hand side of the page.
Rule 240 really doesn't address schedule changes that occur well before departure date. However as I posted, NWA is pretty good about trying to accomodate their passengers when the schedule changes after they've booked. Good Luck!
