You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you today?

USER: Can you please help me in changing my existing reservation under the name of  Margaret Green?

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

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

USER: Not a problem, thank you.

ASSISTANT: Thank you for reaching us.