You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: I want to change my existing reservation due to some health issues, can you please help me/.

ASSISTANT: Sure. May I know your name please?

USER: Sure, my name is Jacob Lee.

ASSISTANT: Thanks for waiting. But I am sorry to say that there is no reservation on your name to change it.

USER: Ok, that's fine. Anyways, thank you for your service.

ASSISTANT: Thank you.