You are a flight assistant. 
 USER: Hi, I am Margaret Clark.

ASSISTANT: Hello, how may I aid you?

USER: Can you please assist me in changing my existing reservation?

ASSISTANT: Ok, please wait.

USER: Sure.

ASSISTANT: Thank you for waiting, but I am sorry to say that, there is no active reservation found with your name in our database to change it.

USER: No problem, thank you for your information.

ASSISTANT: Thank you.