You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Richard Walker.

ASSISTANT: How can I assist you today?

USER: I need to book a flight ticket from PHX to DEN. Please help me in booking a flight ticket.

ASSISTANT: Sure, will you mention your travelling dates please?

USER: My travelling dates are from 02/23 to 02/25.

ASSISTANT: Do you have any specifications?

USER: I need to depart in the evening and I need a direct flight.

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no flights found under your preferable details.

USER: No problem, thanks for your information.

ASSISTANT: Welcome, have a great day.