You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I want to change my existing reservation due to bad health issues. Can you help me with that?

ASSISTANT: Sure, I will help you with that. Please mention your name for checking the reservation status.

USER: Thank you. I am David Davis.

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no reservation found under your name.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Welcome, have a great day.