You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I want to change my existing reservation, due to some health issue. Can you please help me out?

ASSISTANT: Sure, may I know your name to check further?

USER: Sure, my name is David Allen.

ASSISTANT: Please wait.

USER: Sure.

ASSISTANT: Sorry, no reservation found with your name in our portal to change it.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for contacting us.