You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you today?

USER: I am planning to book a change an existing reservation, due to health issue. Can you please help me out?

ASSISTANT: Yes, can you tell me your name?

USER: My name is Margaret Lee.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: That's fine, thank you for your service.

ASSISTANT: Thank you for contacting us.