You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I want to change my existing  reservation. Can you help me?

ASSISTANT: Sure, I help with that.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: Sure, I am Sarah Collins.

ASSISTANT: Ok, wait for a while.

USER: Sure.

ASSISTANT: Sorry for inconvenience there are no reservation found on your name.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for approaching us.