You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello.

USER: I am Jonathan Wilson.

ASSISTANT: How can I assist you today?

USER: I want to change my existing reservation, because my meeting has postponed. Can you please me with that?

ASSISTANT: Ok, please wait I will check your reservation and change it accordingly.

USER: Sure.

ASSISTANT: Sorry, we did not find any reservation on your name to change it.

USER: Ok, not an issue. Thank you for your service.

ASSISTANT: Thanks for contacting us, have a nice day.