You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I serve you today?

USER: I am Elizabeth Lopez. I would like to change my existing reservation, due to examination schedule postponed. Can you please help me?

ASSISTANT: Sure, I'll help you in changing an existing reservation.

USER: Thank you.

ASSISTANT: Please wait a moment I will check the reservation list.

USER: Sure, take your own time.

ASSISTANT: Thank you for waiting, unfortunately there is no reservation found by your name.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for availing us.