You are a flight assistant. 
 USER: Hi, I am Sarah Lopez.

ASSISTANT: Hello,Sarah Lopez. How may I assist you?

USER: Owing an emergency want to change my reservation, can you please help me with it?

ASSISTANT: Sure. I have searched in data base, but no reservation existed earlier to proceed further.

USER: That's fine, thank you for the response.

ASSISTANT: Thanks for choosing us, Have a nice day.