You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I want to change my existing reservation, due to sudden work at my office. Can you please help me with this?

ASSISTANT: Sure, may I know your name?

USER: Sure, I am Charles Nelson.

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: There is no reservation found with your given name.

USER: Ok, Thank you for your help.

ASSISTANT: Thank you.