You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my reservation, due to some health issues I am unable to travel those dates, can you please change my reservation?

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thanks.

ASSISTANT: Ok, may I know your name?

USER: Sure, my name is Eric Carter.

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

USER: Oh! It's ok no problem. Thank you for your information.

ASSISTANT: Ok. Welcome. Thank you for choosing us.