Hello.
Hello. How can I aid you?
I want to change my existing reservation. Could you help me with that?
Sure, I can help  you out. May I know your name?
Benjamin Hall here.
Give me a minute.
Ok.
  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.
That's ok, no problem. Thank you.
Thank you for picking  us.