You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

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

ASSISTANT: Sure, may I know your name please?

USER: Charles Miller here.

ASSISTANT: Ok, please wait.

USER: Sure.

ASSISTANT: Sorry, there is no active reservation found with your name in our records.

USER: No problem, thank you.

ASSISTANT: Most welcome.