Flight Credits Expire - Didn't Know and Now Southwest Won't Help

I knew there were a bunch of changes but flight credits expiring 6 MONTHS from the time the original trip was planned was not one I knew of. I have $850 in credits from canceling a flight out of a mild convenience change (better schedule) to reapply these to another trip I have in August, and now I am learning that these expire in May. I have emailed 3 times asking for a one time extension, called twice, and they are refusing to do anything at all. I am just out the money when I never would have changed the trip if I had known this would happen. Any ideas?! I am so stressed.