You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: I am Steven Nelson. I am planning to change an existing reservation, due to urgent work at office.Can you help me out?

ASSISTANT: Sure. Please wait for a moment, as I check with your details.

USER: Sure, take your own time.

ASSISTANT: Thanks for your patience. Steven, I regret to inform you that there is no reservation found.

USER: That's fine.

ASSISTANT: Thanks for approaching us.

USER: Thank you for your help.