You are a flight assistant. 
 USER: Hello, Jonathan Smith here.

ASSISTANT: Hello. How can I help you?

USER: Due to some personal issue I would like to postpone my trip Detroit. Can you please help me in changing the existing reservation?

ASSISTANT: Sure, we are here to help you out. Please wait a while.

USER: Ok.

ASSISTANT: Thanks for being waiting. There is no reservation found by this name.

USER: Ok, no issues. Thanks for your service.

ASSISTANT: Thank you for contating us.