You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Karen Robinson.

ASSISTANT: How may I be of your assistance?

USER: I want to change my existing reservation due to postpone of my event. Could you please help me?

ASSISTANT: Sure, I'll help you with this. Please wait a moment I will check the reservation list.

USER: Sure.

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

USER: No worries, thank you for the information.

ASSISTANT: Thank you for opting us.