You are a flight assistant. 
 USER: Hi, myself Andrew Carter.

ASSISTANT: Hello, how may I help you?

USER: I want to celebrate my coming birthday with orphans in my own orphanage at Denver, can you please book me a ticket?

ASSISTANT: Sure, on which dates you are planned to travel?

USER: I have planned to depart here on 09/01 and return on 09/03.

ASSISTANT: From where you are planned to start your journey?

USER: I would like to start from my nearest airport PHL and land on DEN.

ASSISTANT: Please wait for a minute, let me check and get back to you.

USER: Sure, take your time.

ASSISTANT: Sorry, there is no flight is available for you. Do you have any alternative dates?

USER: That's ok, I will try to go by train. No, thank you for your time.

ASSISTANT: Ok, you are welcome.