You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: For changing your reservation, we need to know your name to check your reservation status. Can you please provide me your name?

USER: I am Catherine Lewis.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry to say that, we have not found any reservation on your name in our database.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for choosing us.