You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I have a unplanned trip dates in previous reservation, now my done with perfect travelling dates.Can you change my existing reservation?

ASSISTANT: Sure, May I know your name to change?

USER: Please, check the reservation details on Donald Hernandez.

ASSISTANT: Please hold a moment. I will check the status and let you know.

USER: OK.

ASSISTANT: Thank you for waiting. There was no reservation found with your name.

USER: It's my pleasure. That's ok.

ASSISTANT: Thank you for connecting with our service.

USER: Thank you for your help.