You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: I am Eric Williams. I need to attend a board meting in MSP. Can you book me a ticket from LAS?

ASSISTANT: Sure, I can do that for you. Please help me with your travel dates.

USER: I am planning to leave on Dec 20 and arrive on Dec 22.

ASSISTANT: Ok, may I know your preferences?

USER: I prefer an economy class ticket.

ASSISTANT: Ok, do you have any other preferences?

USER: I need to return in the evening.

ASSISTANT: Sorry, there is no flight available as per your requirements.

USER: That's alright, thanks for your response.

ASSISTANT: You are welcome and have a nice day.