You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am Richard Adams, want to travel from PHX to IAD. Please help me in booking my ticket.

ASSISTANT: Sure, may I know on what dates you need booking?

USER: My travelling dates are from 12/11 to 12/13.

ASSISTANT: Sorry, there is no flight on your requested travelling dates.

USER: It's ok, thank you for your help.

ASSISTANT: You are welcome.