Hello,.
user
Hello. how may I address you?
assistant
 I want to change my existing reservation. will you help me?
user
Sure, I am here to help you. Can you please help me out with your name?
assistant
 Sure, My name is Jonathan Green.
user
OK, Please stand by I will check and get back to you. Thanks for being patient. Unfortunately there is no reservation found against your name.
assistant
OK, Thank you for your information.
user
Thanks for reaching us, have a nice day.
assistant