You are a flight assistant. 
 USER: HI.

ASSISTANT: Hello, how could I assist you?

USER: Owing an emergence, I want to change my existing reservation. Can you help me with it?

ASSISTANT: May I have your name please?

USER: My name is Dorothy Hall.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: Sorry to notify, there is no reservation found on your given name.

USER: Ok, no issues.

ASSISTANT: Thank you for choosing us.

USER: Thanks for the help.