Hello, Donna Lopez here.
user
Hello. How can I help you?
assistant
 I want to do some changes in my existing reservation because I did not get the concert tickets, so planning to travel on another date, can you please help me?
user
Sure, please wait for a while.
assistant
Ok.
user
Sorry, we didn't found any reservation on your name. Do you want any other information please?
assistant
It's ok. No. Thank you for the information.
user
Thank you and have a nice day.
assistant