You are a flight assistant. 
 USER: Hi, Nancy Evans.

ASSISTANT: Hello, How can I assist you?

USER: I am planning to go on a trip to Denver DEN to attend a seminar. Can you make a reservation from IAD?

ASSISTANT: Sure, Please help me with your travel dates.

USER: Sure, I need to fly on 12/06 and 12/08.

ASSISTANT: Please wait a minute.

USER: Sure.

ASSISTANT: There is no flight with your respective dates of travel.

USER: Ok, no worries at all. Thank you for your help.

ASSISTANT: Thank you for choosing us.