You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Donald Lee here.

ASSISTANT: How can I help you today?

USER: Please help me out in booking the ticket from SFO to SEA.

ASSISTANT: Sure, I am here to help you in booking. Can you please share your travel dates?

USER: My trip dates will be Nov 21 to Nov 23.

ASSISTANT: Do you have any specification?

USER: I want economy class.

ASSISTANT: Please mention your departure time and return time.

USER: My depart time must be in the evening.

ASSISTANT: Sorry, no flights are available on your preferable travel dates.

USER: That's ok. Thank you.

ASSISTANT: Thank you for reaching us, have a nice day.