You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I serve you today?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, may I know your name please?

USER: I am Janet Allen.

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

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for choosing us.