You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Please book me a flight ticket from IAH to PHL to meet my family.

ASSISTANT: May I know your desired travel dates please?

USER: I have planned to travel on Aug 16th and return on Aug 18th.

ASSISTANT: Do you have any other specifications?

USER: I like direct flight.

ASSISTANT: May I know your name please?

USER: Patrick King.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for opting us.