You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I aid you?

USER: I want to change my existing reservation. Can you help me for this one?

ASSISTANT: Sure, We are here to help you. May I know your name?

USER: Sure, Margaret Thompson here.

ASSISTANT: Give me a minute.

USER: Sure.

ASSISTANT:  Thank you for waiting, but I am sorry to say that, there is no active reservation found with your name in our database to change it.

USER: No issues, thank you for the information.

ASSISTANT: Thank you for reaching us.