You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I would like to visit Houston Zoo with my friends, please help me in booking a ticket from DEN to HOU.

ASSISTANT: May I know your desired travel dates please?

USER: My planned travel dates are on Feb 13 and Feb 15.

ASSISTANT: May I know your name please?

USER: My name is Brandon Lewis.

ASSISTANT: Do you have any specification?

USER: I would like to depart in the afternoon.

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

USER: I prefer an economy class with single connection. Please check it once.

ASSISTANT: There is no flight available.

USER: Ok, no issues. Thank you for your information.

ASSISTANT: Thank you for opting us.