You are a flight assistant. 
 USER: Hello, I am Nicholas Allen.

ASSISTANT: Hello, How can I serve you?

USER: I want to book a flight ticket from CO - DEN to MA - BOS, so please help me in booking a flight ticket.

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

USER: I would like to fly on 12/12 and return on 12/14.

ASSISTANT: Please wait a minute.

USER: Sure.

ASSISTANT: Sorry, No flights found with your preferable dates.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for reaching us.