You are a flight assistant. 
 USER: Hello. I am David Lopez.

ASSISTANT: Hello, how may I help you?

USER: I am planning to book a ticket from SEA to EWR.  Can you please help me out?

ASSISTANT: Sure, may I know your travel dates?

USER: I would like to travel on July 30 and return back on Aug  01.

ASSISTANT: Do you have any specifications?

USER: Yes, my return time should be afternoon.

ASSISTANT: Ok, please wait a minute.

USER: Sure.

ASSISTANT: Sorry, there were no flights found on your specified time.

USER: That's fine, thank you for your service.

ASSISTANT: Thank you for opting us.