You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: Can you please help me to change my existing reservation?

ASSISTANT: Sure, may I know your name to check for the previous reservation?

USER: Sure, my name is Rachel Campbell.

ASSISTANT: Please allow me a moment.

USER: Ok.

ASSISTANT: There is no reservation found under your name.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: Thank you for contacting us.