You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you?

USER: I need to change my reservation due to urgent meeting, can you help me?

ASSISTANT: Sure, may I know your name to check your reservation from our database.

USER: I am John Martin.

ASSISTANT: We regret to inform you that there is no active reservation found on your name to change.

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

ASSISTANT: Thank you.