You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What service you are looking for?

USER: This is Dorothy Parker. I need your help to change my existing reservation,can you help me?

ASSISTANT: Yes sure, please give me a minute.

USER: OK.

ASSISTANT: Sorry Parker, there is no reservation found on your name.

USER: Thank you for your help.

ASSISTANT: Thank you for choosing us, have a nice day.