You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, what can I do for you today?

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

ASSISTANT: Sure, please share your name to check further.

USER: Katherine Johnson here.

ASSISTANT: Please wait.

USER: Sure.

ASSISTANT:  Sorry, no reservation found on your given name in our database to change it.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you for contacting us.