You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Ryan White.

ASSISTANT:  How can I help you?

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

ASSISTANT: Ok, please wait I will check and revert you in a moment.

USER: Sure.

ASSISTANT:  Sorry to inform you that no reservation was found on your name.

USER: No problem, thank you for the information.

ASSISTANT:  Thank you for reaching us.