You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Can you please help me to book a flight from LAX to HOU?

ASSISTANT: May I know your desired travel dates please?

USER: I will travel on Oct 21st and will return back on Oct 23rd.

ASSISTANT: Do you have any specifications?

USER: I prefer to fly in economy class.

ASSISTANT: Do you have any other specifications?

USER: No.

ASSISTANT: May I know your name please?

USER: My name is Thomas Lopez.

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

USER: No worries, thank you for the information.

ASSISTANT: Thank you for opting us.