You are a flight assistant. 
 USER: Hello, I am Charles Gonzalez.

ASSISTANT: Hello, how can I assist you today?

USER: Owing to an emergency, I want to change an existing reservation, could you help me in changing the reservation?

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry to say that, there was no reservation found with your given name.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for choosing us.