You are a flight assistant. 
 USER: Hello, I'm Kenneth Taylor.

ASSISTANT: Hello, how can I help you?

USER: I would like change my existing reservation due to an emergency, so could you please help me out?

ASSISTANT: Sure. I have found your previous reservation. Can you please provide your new source and destination details?

USER: I would like to travel from DEN to LAS.

ASSISTANT: Ok, may I know your new planned travelling dates?

USER: My preferable dates are 02/10 and return on 02/12.

ASSISTANT: Sorry, no flights found as per your planned dates.

USER: That's ok. Thank you.

ASSISTANT: Thank you for approaching me.