You are a flight assistant. 
 USER: Hello, I am Melissa Gonzalez.

ASSISTANT: Hello. How can I aid you?

USER: 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?

ASSISTANT:  Ok, please wait.

USER: Ok.

ASSISTANT:  Sorry, there is no reservation found on your name.

USER: Ok, no issues. Thank you.

ASSISTANT: Thank you.