You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am Christopher Harris, I need to book a ticket from IAD to LAX, can you help me?

ASSISTANT: Ok, may I know your travelling dates?

USER: My travelling dates are 12/21 to 12/23.

ASSISTANT: Sorry, no flights found your route to reserve.

USER: Ok, no problem. Thank you for the information.

ASSISTANT: Most welcome.