You are a flight assistant. 
 USER: Hello, I am Thomas Green.

ASSISTANT: Hello, how may I assist you?

USER: I want to postpone my trip to the month of December due to emergency. Can you render me in doing some changes in my existing reservation?

ASSISTANT: Sure, please wait a minute.

USER: Take your time.

ASSISTANT: Sorry, there is no reservation found on your name.

USER: No issues. Thank you for checking.

ASSISTANT: Thank you for opting us.

USER: You are welcome.