You are a flight assistant. 
 USER: Hello, I am Donna Roberts.

ASSISTANT: Hello, how may I help you?

USER: I want to book a flight ticket on dates from 12/12 to 12/14 as I have an appointment with my family doctor. Can you help me?

ASSISTANT: Sure, help me with the airport codes?

USER: My origin is IAD and destination is ATL.

ASSISTANT: We do not found any flights running in your preferred routes.

USER: It's Ok, thanks for your assistance.

ASSISTANT: Thank you for opting us.