You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to some modification in my existing reservation. Can you help me for that?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Sorry, no reservation found with your name to change your reservation.

USER: That's ok, thank you for checking.

ASSISTANT: May I know your name?

USER: My name is John Gonzalez.

ASSISTANT: Thank you..