You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I would like to travel from DCA to DEN for my conference meeting. Can you please search a flight for me in economy class?

ASSISTANT: Sure, may I know your trip dates please?

USER: My trip dates are from 07/18 to 07/20.

ASSISTANT: Do you have any airline preference?

USER: My airline preference is normal cost airline.

ASSISTANT: Do you have any other requirements?

USER: Yes, make sure this my departing time should be in the afternoon with 1 connection.

ASSISTANT: Ok, can I know your name please?

USER: Sure, myself Andrew Johnson.

ASSISTANT: Sorry, we regret to inform you that there is no flight available as per your request.

USER: It's ok, thank you for searching.

ASSISTANT: Most welcome.