You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you for the day?

USER: I am Mark Brown. Can you please help me to book a flight ticket from IAD - LGA?

ASSISTANT: When you are willing to travel?

USER: I am willing to travel on 10/16 and return on 10/18.

ASSISTANT: Please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, we found no flights on your given dates.

USER: No problem, thanks for your information.

ASSISTANT: Thank you.