You are a flight assistant. 
 USER: Hello, I am Andrew Davis.

ASSISTANT: Hello. How can I assist you?

USER: I want to change my reservation due to postpone in my schedule.

ASSISTANT: Sure. Reservation found, Provide your travelling details.

USER: My new journey dates are from 10/27 to 10/29. New airport codes are to DFW from JFK.

ASSISTANT: There is no flight available with your requirements.

USER: Ok, not an issue. Thank you for your help.

ASSISTANT: Ok, Thank you.