You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

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

ASSISTANT: Ok, may I know your name.

USER: I am Joshua Brown.

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

USER: That's ok. Anyways, thank you.

ASSISTANT: Thank you for contacting our agency.