You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. May I know your name please?

USER: I am Raymond Thomas.

ASSISTANT: How can I help you Raymond?

USER: I need your help for change my existing reservation, can you help me?

ASSISTANT: Sure. Please give me a minute so that I can check the details.

USER: OK.

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

USER: Thank you for your help.

ASSISTANT: Thank you for choosing us.