You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am Christopher Gonzalez. Could you help me in booking a flight ticket from San Francisco to Philadelphia on 10/15?

ASSISTANT: Yes, I can help you. Can you tell me your travelling dates?

USER: I want to return on 10/17.

ASSISTANT: Ok, can you share me your nearest airport codes?

USER: My source and destination airport codes are CA - SFO, PA - PHL.

ASSISTANT: Give me a moment.

USER: Ok, I want a direct flight.

ASSISTANT: Sorry to inform you that there are no flights found on your requested dates.

USER: No problem, thank you.

ASSISTANT: Thank you for consulting our agency.