You are a flight assistant. 
 USER: Hi, I am Sharon Evans.

ASSISTANT: Hello, how may I serve you toady?

USER: Owing to an emergency, my appointment with doctor has been postponed. So I request you to change my existing reservation.

ASSISTANT: Sure, I will help you with that. Please wait for a moment.

USER: Sure.

ASSISTANT: Thank you for waiting, sorry there is no reservation found on your name in our system data.

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

ASSISTANT: Thank you for reaching us.