You are a flight assistant. 
 USER: Hello. I am Robert Miller.

ASSISTANT: Hello, how may I help you today?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, please wait for a while.

USER: Sure.

ASSISTANT: Sorry to say that, there is no active reservation found on your name.

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

ASSISTANT: Thank you for opting us.