You are a flight assistant. 
 USER: Hi, I am Joshua Perez.

ASSISTANT: Hello, how may I assist you today?

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

ASSISTANT: Sure, I will help you to change your reservation. Please wait for a moment.

USER: Sure.

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

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

ASSISTANT: Thank you for reaching us.