You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I have changed my trip, so please help me to change my recent reservation.

ASSISTANT: May I know your name?

USER: My name is Karen Walker.

ASSISTANT: Karen please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, no reservation found by your name.

USER: Its ok, no problem. Thank you for the information.

ASSISTANT: Thank you for contacting us.