You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Melissa Scott.

ASSISTANT: How can I assist you?

USER: I am planning to visit San Francisco, can you please book me a ticket from IAD to SFO?

ASSISTANT: Sure, may I know your journey dates please?

USER: My preferable journey dates are from 03/09 to 03/11.

ASSISTANT: Please be on hold.

USER: Sure.

ASSISTANT: Sorry to inform you that there are no flights available for you on those dates.

USER: Ok, not an issue. I will find any alternate for this trip. Thank you for providing information.

ASSISTANT: Thank you for choosing us.