You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello. How may I help you at this minute?

USER: Can you please help me in booking my flight ticket from IAD to EWR?

ASSISTANT: Ok, I am here to help you with that. Can I know your planned trip dates?

USER: My planned travel dates are April 15-17.

ASSISTANT: May I know your class preference?

USER: I do not have any preferences.

ASSISTANT: Can I know your good name?

USER: Myself, John Allen.

ASSISTANT: Ok, please wait for a minute.

USER: Ok.

ASSISTANT: Sorry to say that, there are no flights available based on your journey dates.

USER: Ok, no issues. Thank you for your service.

ASSISTANT: Thank you for approaching us.