You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: My name is Karen Thomas.

ASSISTANT: How may I help you?

USER: Owing to emergency, I need to change my existing reservation. Please help me in that.

ASSISTANT: Please hold on a moment.

USER: Sure.

ASSISTANT: Thanks for your time, there is no reservation found on your name to change it.

USER: No problem, thanks for your information.

ASSISTANT: Thanks for choosing us, have a good day.