You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I want to change my flight ticket reservation as my business meeting is been postponed to some other date. Can you change it?

ASSISTANT: Ok, may I know your name?

USER: I am Dennis Lee.

ASSISTANT: Ok, I have found your reservation. Can you please mention your traveling dates?

USER: My travel dates for the journey are 12/20 to 12/22.

ASSISTANT: Ok, may I know your source and destination airport codes?

USER: The airport codes for the journey would be from LGA to ATL.

ASSISTANT: Sorry, no flight found on your preferable dates tio change.

USER: Ok, not a problem. Thank you.

ASSISTANT: Most welcome.