You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I aid you?

USER: I need to change my existing reservation as my exams got postponed, Can you please help me with that?

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

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

ASSISTANT: Thank you for reaching us.