You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am planning to change my trip dates. Can you please help me to change my existing reservation?

ASSISTANT: Yes, can I know your name?

USER: My name is William Phillips.

ASSISTANT: Ok. Sorry to inform you that there is no reservation found on your name. Thank you for reaching us.

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