You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you today?

USER: I am planning a trip to Las Vegas and I would like to depart in the afternoon time. So can you book the flight ticket for me?

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

USER: The travel dates would be from July 28 to July 30.

ASSISTANT: Please provide your airport codes.

USER: My airport codes are from DFW to LAS.

ASSISTANT: Do you have any specifications?

USER: I would like to prefer a single connecting flight.

ASSISTANT: Do you have any other preferences?

USER: No.

ASSISTANT: Please provide your name.

USER: I am Scott Smith.

ASSISTANT: There are no flights found under your preferable details.

USER: Not a problem. Thank you.

ASSISTANT: Welcome, have a great day.