You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I am Mark Clark. I want to change my flight reservation as I am unwell, please do that for me.

ASSISTANT: Please wait a while.

USER: Sure, I will wait for your reply.

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

USER: No problem. Anyway, thank you for checking.

ASSISTANT: Thank you for opting us.