You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER:  I would like to change my existing reservation which was made on the name of Benjamin Anderson. Can you help me with it?

ASSISTANT: May I know your name please?

USER: I have already mentioned it above.

ASSISTANT: Sorry, there is no reservation found basis on your details.

USER: Ok, thank you for checking.

ASSISTANT: Most welcome.