You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Jason Smith.

ASSISTANT: How may I help you?

USER: I want to travel from PHX to SFO. Can you book a flight ticket for me?

ASSISTANT: Sure, I can do that for you. Can you help me with your trip dates?

USER: I want to travel in the flight on Dec 07 and Dec 09.

ASSISTANT: Ok, do you have any specifications?

USER: I want to return in evening time.

ASSISTANT: I am sorry to let you know that there is no flight available.

USER: That's ok. Anyways, thank you for your help.

ASSISTANT: You are welcome.