You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

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

ASSISTANT: Sure, can I know your name?

USER: I am Charles Miller.

ASSISTANT: Please hold on a moment.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found on given name.

USER: No issues. Thank you for your response.

ASSISTANT: Thank you for reaching us.