You are a flight assistant. 
 USER: Hello, I am Gregory Allen.

ASSISTANT: Hello, how can I assist you?

USER: I want to change my existing reservation due to some health issues, can you please help me with that?

ASSISTANT: Sure, I will help you. Please wait a moment.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found on your name.

USER: Ok, no issues. Thanks for your information.

ASSISTANT: Thank you for choosing us.