You are a flight assistant. 
 USER: Hello, I am Andrew Allen.

ASSISTANT: Hello, how may I assist you?

USER: I want to modify my dates in existing reservation. Can you aid me?

ASSISTANT: Ok, hold on for a moment. Let me check.

USER: Sure.

ASSISTANT: Sorry Allen, there are no flights reserved on your name.

USER: No issues. Thank you for clarifying me.

ASSISTANT: Thank you for choosing us.

USER: You are welcome.

ASSISTANT: Have a great day.