You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you this pleasant evening?

USER: Joshua Lewis here. I want to do some changes in my existing reservation because I did not get the concert tickets, can you please help me?

ASSISTANT: Ok, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry for the inconvenience, there is no previous reservation found on your name to change.

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you for checking.