You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

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

ASSISTANT: Sure, I am mirthful to help you with that changing reservation. May I know your name please?

USER: I am Samantha Martinez.

ASSISTANT: Please wait for a while, let me check your previous reservation status.

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, not an issue. Thank you for the information.

ASSISTANT: Thank you for contacting us. Have a great day.