You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you today?

USER: Owing to an emergency, my appointment with doctor got postponed. So I want you to change my existing reservation.

ASSISTANT: Ok, may I know your name please?

USER: Sure, William Moore.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, there was no reservation found with your given name.

USER: Ok, no worries at all. Thank you for your service.

ASSISTANT: Thank you for opting us.