You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Sarah Harris.

ASSISTANT: How may I aid you today?

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

ASSISTANT: Please wait a moment, let me check in our database.

USER: Sure.

ASSISTANT: Sorry Harris, there is no reservation found on your name.

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

ASSISTANT: Thank you for reaching our service.