I've had similar problems with them and I've gotten nowhere with them (also through Expedia). Thankfully, changes on my tickets were not major, so it was fine in the end.

Have you tried calling them directly? If you get any luck with them directly, do a 3-way call with them and with Expedia to see what they say.

This is one airline whose IT and backend and customer service majorly sucks (not much different from other Spanish airlines though).