You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you today?

USER: I am Kimberly Carter and I want to change my existing reservation.

ASSISTANT: Sure, please stand by I will check and revert you.

USER: OK.

ASSISTANT: Thanks for waiting. Unfortunately there is no reservation found against your name.

USER: Thank you.

ASSISTANT: Thanks for reaching us, have a nice day.