Log on to LAN.com, and click on the "Reservations and Services" link in the navigation bar at the top of the home page. Move your cursor to the bottom right-hand corner of the new page, and click on the image of a calendar and the "Flight Changes" icon.
Type the reservation code and passenger's surname into the two boxes displayed, and click "Continue." Enter the new travel date, and follow the onscreen instructions to complete the process. If the price of the ticket has changed, you must pay the difference with a debit or credit card. Payment must be confirmed before the revised flight ticket is issued.
Print two copies of the new itinerary, and ensure that any accommodations or car rental booked for the original date is also changed to the new date.