You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: My name is Rachel Clark.

ASSISTANT: How can I help you?

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

ASSISTANT: Please wait a while.

USER: Sure.

ASSISTANT: Sorry to say, there is no reservation on your name in our database.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for opting us.