You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I serve you today?

USER: Due to some health issue, I need to change my existing reservation.

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: My name is Donald Walker.

ASSISTANT: Ok, please be on hold.

USER: Sure.

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

USER: Not an issue, thank you for checking.

ASSISTANT: Thank you for opting us.