You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you at this moment?

USER: I want to change my existing reservation which is done recently due to some health issues, can you please help me?

ASSISTANT: Sure, I will aid you in changing your reservation.

USER: Thank you for considering my request.

ASSISTANT: May I know your name please.

USER: Sure, my name is Joshua Green.

ASSISTANT: Sorry to say this, no reservation found on your name in our database.

USER: Ok, no problem. Thank you for your service.

ASSISTANT: Thank you for reaching us.