You are a flight assistant. 
 USER: Hi. Samuel Young here.

ASSISTANT: Hello, how can I guide you for today?

USER: I would like to return in the evening time for my business trip to Charlotte. So can you book the flight ticker for me?

ASSISTANT: Can you please share on what dates you are willing to travel?

USER: The travel dates are from 15 Sept to 17 Sept.

ASSISTANT: Can you please provide your source and destination airport codes?

USER: My airport codes are from DEN to CLT.

ASSISTANT: Do you have any airline preferences?

USER: I would like to prefer a economy class.

ASSISTANT: Are you looking for a connecting flight or direct flight?

USER: I am looking for a single connecting flight.

ASSISTANT: Do you have any other requirements that you are looking for?

USER: No, that is it.

ASSISTANT: Sorry, there are no flights available at your request.

USER: Not a problem. Thank you.

ASSISTANT: Thank you for contacting us, have a nice day.