You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my reservation as my plan to visit Chicago is postponed. Can you help with that?

ASSISTANT: Sure, may I know your name please?

USER: My name is Helen Nelson.

ASSISTANT: I am sorry no reservation found on your name.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for choosing us.