You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: My name is William Jackson. Can you please help me to change my existing reservation?

ASSISTANT: Sure, we are here to help you with this reservation  change.

USER: Sure.

ASSISTANT: Please wait for a moment, let me check your previous reservation status.

USER: Sure.

ASSISTANT: Thank you for waiting. There is no active reservation found with your name in our database to change it.

USER: No problem, thank you.

ASSISTANT: Thank you for reaching us.