Title says it all really...

Have a ticket booked via Expedia.com and need to change first leg to earlier flight but same day (3pm instead of the 6pm booked). After 40 min with Expedia tying to change it and then given some ridicluous amount for a fare difference, I wonder at what point it becomes EKs to change?

There is plenty of Avail per Expertflyer so dont think that will be an issue.