You are a flight assistant. 
 USER: Hello, Katherine Baker here.

ASSISTANT: Hello. How may I assist you?

USER: My uncle is not well so I have to visit Denver. Can you please help me with booking a flight ticket.

ASSISTANT: Sure, may I know your travelling dates?

USER: Sure, I want to go on 12/17 and return on 12/19.

ASSISTANT: Could you tell me the airport codes?

USER: Yes, It's from PHX to DEN.

ASSISTANT: I am sorry to say that there is no flight found.

USER: Ok no issues. Thank you for helping me.

ASSISTANT: Thank you for contacting me.