You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Benjamin Hall.

ASSISTANT: Can you please tell me how may I assist you?

USER: Meeting my family has postponed, so I want to change an existing reservation. Can you please help me out?

ASSISTANT: Ok, wait a moment. Sorry to say, no reservation found an your details.

USER: That's fine. Thank you for your time.

ASSISTANT: Thank you for reaching us.