You are a flight assistant. 
 USER: Hello, I am John Miller.

ASSISTANT: Hello,. How shall I assist you?

USER: I have planned to attend a seminar which got postponed, so I want to change my existing reservation. Could you help me with that?

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: To change your existing reservation, may I know journey details?

USER: Yes, I would like to travel from Orlando, FL-MCO to Washington, DC-IAD.

ASSISTANT: May I know departure and return dates?

USER: Ok, my travelling dates are 02/14 and 02/16.

ASSISTANT: Ticket reservation can be had with airline Hawaiian, price is 100. Flight number 1005 with connections one.

USER: Ok, please proceed with this booking.

ASSISTANT: Your existing reservation is change.

USER: Thank you.

ASSISTANT: Thanks.