You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: I am Karen Lee, want to alter my recent reservation due to some emergency. Please help me out with that.

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Please wait a minute.

USER: Ok.

ASSISTANT: Sorry Karen, there is no active reservation found under your name in our records.

USER: It's ok, thank you for your help.

ASSISTANT: Most welcome.