You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello. How can I aid you?

USER: My name is Gregory Perez. Please change my existing reservation.

ASSISTANT: Sure. Wait for a moment, I will check and revert to you.

USER: Ok.

ASSISTANT: Thanks for waiting. Unfortunately, There is no reservation found with your name.

USER: Thanks.

ASSISTANT: Thanks for reaching us.