You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you?

USER: Your agency have booked a ticket with wrong dates, so I want to change my reservation, can you help me?

ASSISTANT: Sure, I will help you. May I know your name please?

USER: I am Dennis Collins.

ASSISTANT: Dennis, no reservation has been found on your name in our database.

USER: No problem, thanks for checking.

ASSISTANT: Thank you for choosing our service.