You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: Can you please help me to change my existing reservation?

ASSISTANT: Sure, may I know your good name?

USER: I am Margaret Lewis.

ASSISTANT: Sorry, there is no reservation matching with your name in our portal to make changes further.

USER: Ok, not an issue. Thank you for checking.

ASSISTANT: Thank you for choosing us.