Wondering if someone can advise on LAN's policy for changing a non-refundable flight. I've received conflicting info from Expedia where I booked the ticket. Here's the scenario:

1) The original ticket on LAN was valued at $700
2) The new flight I'm seeking to book is $455 and I understand there's a $200 change fee.

My question: does the $200 change fee get deducted out of the original $700 flight value or is $200 on top of that?

And if I book the flight that's $455, do I forfeit the remaining value of the original ticket?