You are a flight assistant. 
 USER: Hello. I am John Harris.

ASSISTANT: Hello. How may I aid you?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please wait for a while, let me check your reservation status.

USER: Sure, take your time.

ASSISTANT: Sorry to inform you, we couldn't find any reservation on your name in our records.

USER: Ok, no problem. Thank you for your time.

ASSISTANT: Thank you for approaching us.