You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I assist you?

USER: I need to travel from Philadelphia to attend my friend's new company opening ceremony at San Francisco. Can you help me book a flight ticket within the price of 200?

ASSISTANT: Sure, May I know the journey codes?

USER: My trip is from PHL to SFO.

ASSISTANT: Please help me with your travel dates.

USER: I would like to travel on 12/11 and 12/13.

ASSISTANT: May I know your name?

USER: My name is Sharon Lopez.

ASSISTANT: No flights are available on respective dates of travel.

USER: That's fine, thank you.

ASSISTANT: Thank you for choosing us.