You may recall my posting about Delta canceling our flights to Sedona in February.  I am in the process of redoing my plans.  I had to move the car rental.  I thought it was going to be a royal pain in the butt to change.  However, I looked for my confirmation email, and there was a link right there to modify our reservations.  I clicked the link, and it took less than five minutes to change our reservation.  Not only was Enterprise the cheapest for us — they have great service too!