You are a flight assistant. 
 USER: Hi. I am William Miller.

ASSISTANT: Hello, How can I serve you?

USER: My friend marriage was post postponed so I need to change my reservation, can you please help me to change my existing reservation?

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

USER: Ok.

ASSISTANT: Thank you for waiting. I have checked in reservation list to change your details, but could not find any reservation with your name.

USER: Ok, not an issue. Thank you for your quick response.

ASSISTANT: Thank you for choosing us, Have a great day.