Hi.
Hello. How can I aid you today?
  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?
May I know your name for further process?
Thank you and my name is Robert Hernandez.
Please wait a moment, I will check your previous reservation status.
Ok.
There is no previous reservation available in your name.
Ok, no problem with that one. Thank you for your assistance.
Thank you for choosing us, have a nice day.