You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: Can you help me to change my reservation?

ASSISTANT: Sure, may I know your name please?

USER: I am Dennis Collins.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, we regret to inform you that there is no active reservation found with your name in our records.

USER: No problem, thank you for checking.

ASSISTANT: Most welcome.