You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I made a reservation earlier, but due to some personal issues I want to change my existing reservation. Can you please help me to change my reservation?

ASSISTANT: Sure, may I know your name please?

USER: Sure, I am Dennis Perez.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, no reservation found with your name.

USER: Ok, Thank you for providing information.

ASSISTANT: Thank you for opting us.