You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Charles Parker.

ASSISTANT: How may I assist you now?

USER: I want to do some changes in my existing reservation. Can you help me for that?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Please allow me to check with your existing reservation.

USER: Sure, I will wait for your response.

ASSISTANT: Sorry to say, there is no active reservation by your name.

USER: That's ok, thank you for checking.

ASSISTANT: Have a nice day.