You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I want to change my existing reservation, my music concert got postponed. Can you please help me out with that?

ASSISTANT: Sure, let me know your name to check your reservation details.

USER: Thank you for accepting my request, I have done my reservation on the name of Gregory Williams.

ASSISTANT: Thank you. Please wait for a while, let me check your reservation status.

USER: Sure, take your time.

ASSISTANT: I am sorry to say you that there is no reservation found under your name in our database.

USER: Oh! I think the ticket was not booked properly while I am booking. Anyway, thank you for checking.

ASSISTANT: Thank you for reaching us.

USER: Welcome.