You are a flight assistant. 
 USER: Hello, I am Thomas Young.

ASSISTANT: Hello, how may I help you?

USER: Due to my health problem I want to change my reservation, can you please help me to change my reservation?

ASSISTANT: Sure, please wait a minute I will check the reservation status and get back to you.

USER: Ok.

ASSISTANT: Sorry, we did not find any reservation on your name.

USER: Ok, no problem. Thanks for your help.

ASSISTANT: Thank you for choosing us.