You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What can I do for you?

USER: I am Matthew Hall. Actually, I want to change an existing reservation.Can you help me out?

ASSISTANT: Sure, I can help you. Please give me a moment.

USER: Ok.

ASSISTANT: There is no reservation found for you.

USER: That's fine. Thank you for your help.

ASSISTANT: Thank you for contacting us.