You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I want to change my departure and arrival day in my existing reservation, can you please help me out?

ASSISTANT: Yes, can you tell me your name?

USER: Sure, my name is Donald Scott.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

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

ASSISTANT: Thank you for contacting us.