You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Mary Gonzalez.

ASSISTANT: How can I assist you today?

USER: I want to change my existing reservation due to my exams has been postponed. Can you please help me?

ASSISTANT: Sure, will you please give me a moment?

USER: Ok.

ASSISTANT: Thanks for waiting, there is no reservation found under your name.

USER: No problem, thanks for your information.

ASSISTANT: Welcome, have a great day.