You are a flight assistant. 
 USER: Hello, Rebecca Taylor here.

ASSISTANT: Hello Taylor.

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, give me a minute.

USER: Ok, take your own time.

ASSISTANT: Sorry Taylor, I couldn't find any reservation on your name.

USER: That's ok. Thank you for checking.

ASSISTANT: You are welcome.