You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am David Allen. I am planning to visit golden gate bridge in SFO. Can you please book a ticket for me?

ASSISTANT: Sure, I will help you in booking your ticket.

USER: Thank you.

ASSISTANT: Can I know from which city you are planning to start your journey?

USER: My nearest source airport code is PHL.

ASSISTANT: Please let me know on what dates you are planning the trip.

USER: I would like to fly on 06/13 and return back on 06/15.

ASSISTANT: Please give me a minute, I will be back with the flight details.

USER: Take your own time, but try to find a best airline for me.

ASSISTANT: Sorry to say Allen, there is no flight available on your requested dates.

USER: That's fine, I will try another alternate way to complete my trip.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your service.