You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Anthony Clark here.

ASSISTANT: How may 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: Sure, please wait a moment.

USER: Ok.

ASSISTANT: Sorry, no reservation has been found on your name.

USER: That's fine, thanks for your help.

ASSISTANT: Thank you for using our services.