You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I address you?

USER: Could you please help me to update my travelling dates in my existing reservation?

ASSISTANT: Sure, I can help you. May I know your name to trace your details?

USER: Thank you. I am Robert Harris.

ASSISTANT: Give me  a minute.

USER: Sure.

ASSISTANT:   Thank you for waiting, but I am sorry to say that, there is no active reservation found with your name in our database to change it.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for picking us.