You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you today?

USER: Can you help me change my existing reservation which was made on the name of Dorothy Anderson?

ASSISTANT: Sure, please wait for a moment.

USER: Sure.

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

USER: It's ok, thank you for the response.

ASSISTANT: Thank you for opting us.