You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I be at your service today?

USER: Could you please change my existing reservation due to postpone of my trip?

ASSISTANT: May I know your name please to check the status of your reservation?

USER: I am Helen Collins.

ASSISTANT: Thank you. Please stay online for a while, I will check your reservation status and let you know.

USER: Sure.

ASSISTANT: Sorry, there is no reservation matching with your name in our portal to make changes further.

USER: Not a problem, thank you for the information.

ASSISTANT: Thank you for reaching us.