You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Christopher Smith, I want to book a flight ticket from IAD to LGA.

ASSISTANT: Sure, I will help you out.

USER: Thank you.

ASSISTANT: May I know your travelling dates please?

USER: Sure, my travelling dates are 11/24 and 11/26.

ASSISTANT: Ok, please wait for a while.

USER: Ok, sure please take your time.

ASSISTANT: Sorry, there are no flights found in our database.

USER: Not a problem, anyway thank you for the information.

ASSISTANT: Thank you for choosing us.