You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Edward Lee here.

ASSISTANT: Edward Lee, how may I render you?

USER: I am planning to book a flight ticket to IAD from SFO, can you please help me out? Sure, my planned travelling dates are Jan 11 and Jan 13.

ASSISTANT: Please wait for a while.

USER: Ok, take your time.

ASSISTANT: Sorry, no flights are available on your route.

USER: It's ok, thank you for the information.

ASSISTANT: Thank you for choosing us.