You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

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

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

USER: Myself Charles Williams.

ASSISTANT: Sorry, there is no reservation with your given name.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.