Hello, I am Jack Hernandez.
user
Hello, how can I help you?
assistant
 Owing to an emergency I need to change my existing reservation.
user
Sure, I will find your existing reservation and revert you in a while.
assistant
OK.
user
Sorry for the inconvenience, we were unable to find  a reservation on your name.
assistant
OK.Thank you for your information.
user
Thank you for assisting with us, have a great day.
assistant