One option is to ask Orbitz to authorize you to deal directly with LAN. They can put a note on your booking saying that they give permission, and when the LAN representative sees it, he/she can then work directly with you.

However, I don't think this will do you much good. If they hung up on Orbitz, which is a major travel agency that gives them lots of business, then they aren't likely to have much time to deal with individual passengers.

Unfortunately when airlines cancel flights this type of thing happens. I'm not sure whose fault it is.

If you can't get anything resolved, then just go to check in for your flight a bit early and see if the agent at the counter can sort it out. Sometimes they are more helpful than the call center.