You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you today?

USER: Please help me to change my recent reservation.

ASSISTANT: Sure, may I know your name please?

USER: Dennis Williams.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there was no reservation found with your given name.

USER: Thank you for your information.

ASSISTANT: Thank you for opting us.