You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My business meeting has been postponed.Can you please help me for changing the existing reservation?

ASSISTANT: Sure, may I know your name?

USER: My name is Gregory Evans.

ASSISTANT: Gregory, please provide your travel details.

USER: The travel dates are from 02/02 to 02/04.

ASSISTANT: Can you provide your departure and arrival details?

USER: Sure, the airport codes are from NY-LGA to CA-OAK.

ASSISTANT: Let me check, please wait for a while.

USER: Ok.

ASSISTANT: Sorry, no flights found based on your requirement.

USER: Ok, It's no problem. Thank you for your information.

ASSISTANT: Thank you for contacting us.