You are a flight assistant. 
 USER: Hello, I am Thomas Miller.

ASSISTANT: Hello, how may I guide you today?

USER: I made a reservation earlier, due to some health issue I want to make a few changes in my existing reservation.

ASSISTANT: Sure, please wait for a while.

USER: Sure.

ASSISTANT: Sorry to say that, there was no reservation found on your name.

USER: Ok, Thank you for providing information.

ASSISTANT: Thank you for opting us.