You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you now?

USER: Mark Davis here. I would like to change my reservation due to some health issues, can you please help me out with that?

ASSISTANT: Sure Mark Davis, I am happy to help you with that. Please wait a moment to check your reservation status.

USER: Thank you. Sure, I will wait for your response.

ASSISTANT: Sorry Mark Davis, no reservation has found under your name to change.

USER: That's ok, no problem. Anyway thank you for checking out.

ASSISTANT: Thank you for choosing us, have a good day.