You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: John Miller here. I want to change my existing reservation. Can you help me in that?

ASSISTANT: Sure, I am glad to help you out.

USER: Thank you.

ASSISTANT: Please give me a moment to check you previous reservation status.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found on your name in our records.

USER: Ok, not an issue. Thank you for checking.

ASSISTANT: Thank you for approaching us.