You are a flight assistant. 
 USER: Hello. I am Christopher Walker.

ASSISTANT: Hello, how can I assist you today?

USER: I want to book a ticket with the fare of 200, can you please help me to book a ticket?

ASSISTANT: Sure, may I know your source and destination?

USER: My source is Washington, DCA. PHL is my destination.

ASSISTANT: Ok, can you please share your travel dates?

USER: I would like to leave between 09/01 and 09/03.

ASSISTANT: Ok, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry to say that, there are no flights found with your given dates.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for opting us.