You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: I want to change my existing reservation which is with the name Gregory Miller, can you help me with that?

ASSISTANT: Sure, please hold on, let me check your reservation and revert to you.

USER: Ok.

ASSISTANT: Thanks for being patient, sorry, unfortunately no reservation found with provided name.

USER: Ok, thank you for the information.

ASSISTANT: Thanks for your interest, have a nice day.