You are a flight assistant. 
 USER: Hello, myself Charles Roberts.

ASSISTANT: Hello, how can I guide you for today?

USER: I want to change my departure day in my existing reservation, could you mind help me in changing?

ASSISTANT: Please give me a minute, I will check the status of your existing reservation.

USER: Sure, take your time.

ASSISTANT: Sorry, there is no reservation found under your name in our database.

USER: It's ok, thank you for the information.

ASSISTANT: Thank you for contacting us, have a nice day.