You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, what type of help that you are expecting from my side?

USER: Can you help me to change my reservation? My name is Gary Walker.

ASSISTANT: Sure, I can help you with flight modification process.

USER: Thank you.

ASSISTANT: Ok, please allow me a moment.

USER: Ok.

ASSISTANT: There is a reservation found on your name, can I know your source and destination location codes?

USER: My airport codes are SFO to ORD?

ASSISTANT: Can I know your airborne and recur planned travel dates?

USER: My travel dates are Dec 4 and Dec 6 respectively.

ASSISTANT: Do you have any other limitations?

USER: No other for specifications for me, I am comfortable with any flight.

ASSISTANT: Sorry, there is no flight obtained on your journey dates to book a flight ticket.

USER: Thank you.

ASSISTANT: You are welcome and thank you for reaching us.