You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am Helen Gonzalez. I want to change my reservation due to my trip has been postponed.

ASSISTANT: Ok, please wait a moment I will check and get back to you.

USER: Sure.

ASSISTANT: There is no reservation on your name.

USER: Ok, thank you.

ASSISTANT: Thanks for choosing us.