You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Gregory Smith.

ASSISTANT: How could I aid you today at this moment?

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

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: Unfortunately we did not find any reservation on your given name in our data.

USER: Not a problem, thank you.

ASSISTANT: Thank you for choosing us.