Hi.
user
Hello. How can I aid you today?
assistant
  Due to sudden change in my planned dates of journey, I would like to change my reservation. Can you please help me out with changing of my reservation?
user
May I know your name for further process?
assistant
Thank you and my name is Robert Hernandez.
user
Please wait a moment, I will check your previous reservation status.
assistant
Ok.
user
There is no previous reservation available in your name.
assistant
Ok, no problem with that one. Thank you for your assistance.
user
Thank you for choosing us, have a nice day.
assistant