You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I want to change my existing reservation because of some urgent work.

ASSISTANT: Ok. Let me know your name to change your reservation?

USER: Sure, my name is Charles martin.

ASSISTANT: Ok, please wait for a moment.

USER: Sure, take your time.

ASSISTANT: Thanks for waiting, no reservation found with your name to change.

USER: Ok, no problem.

ASSISTANT: Thanks for approaching us, have a nice day.

USER: Thank you for your service.