You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I aid you?

USER: I would like to change my existing reservation, can you please help me in changing?

ASSISTANT: Sure, we are happy to help you. Please let me know your good name.

USER: Mary Nelson.

ASSISTANT: Sorry, there is no active reservation on your name in our records.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for choosing us.