You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello,. How can I render you today?

USER: Please change my existing reservation.

ASSISTANT: Sure, we are here to help you. Let me know your name to check the reservation.

USER: I am Melissa Allen.

ASSISTANT: Thanks for your name, there is no reservation found on your name.

USER: Thank you.

ASSISTANT: Thank you for reaching us.