You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Benjamin Evans here.

ASSISTANT: Good morning Evans. How can I assist you at this moment?

USER: Unfortunately, I want to change my existing reservation due to some health issues can you please help me in this intent?

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

USER: Sure, take your time.

ASSISTANT: Thank you for waiting.

USER: My pleasure.

ASSISTANT: Sorry Evans, there is no reservation found under your name to change.

USER: Ok, that's fine. Thank you for your information.

ASSISTANT: My pleasure. Thank you for choosing us.