Hello,.
Hello, how may I best support you today?
I made a reservation earlier in the wrong date unknowingly so, I want to change my existing reservation. Can you help me with that?
Sure, may I know your good name to check the reservation?
Ok, I am Patricia Lewis.
Thank you for providing your name, I hardly tried to find  a reservation on your name but could not found any reservation on your name.
Ok, I think the ticket has been reserved with another agency. Thanks for your effort in searching my reservation status.
Thank you for opting our service.