You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What assistance do you require from our agency?

USER: I am planning to change an existing reservation, due to health issue. Can you please help me out?

ASSISTANT: Sure, I am happy to assist you with that. Can I know your name please?

USER: My name is Jonathan Collins.

ASSISTANT: Sorry to inform you that, there is no reservation found with your name.

USER: That's fine, thank you for your service.

ASSISTANT: Most welcome. Thank you for choosing us.