You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: Due to some personal work, I want to change my existing reservation. Can you please help me with this?

ASSISTANT: Sure, may I know your name?

USER: Sure, I am John Brown.

ASSISTANT: OK, please wait a moment.

USER: Sure, I will wait.

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

USER: Ok, Thank you for your service.

ASSISTANT: Thanks for reaching us.