You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: In my existing reservation I need some changes, will you please help me in modifying my details?

ASSISTANT: Sure, please provide the name on which the reservation has been confirmed.

USER: Sure, my name is Michael Mitchell.

ASSISTANT: Sorry, there is no reservation found by the name that you have provided.

USER: That's ok, thank you for the information.

ASSISTANT: Thank you and have a nice day.