You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my existing reservation, as my meeting with client has postponed suddenly. Can you please help me with this?

ASSISTANT: Sure, please wait for a while. Can you please tell your name to check the reservation details?

USER: Yes, I am Laura Johnson.

ASSISTANT: Sorry, there is no reservation found by your name.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you and have a nice day.