You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Joseph Robinson.

ASSISTANT: How can I assist you at this moment?

USER: I want to change my existing reservation due to postpone of my exams, can you help me with that?

ASSISTANT: Sure, I will help you in changing your reservation. Please give me a moment to check your reservation status.

USER: Sure.

ASSISTANT: Joseph Robinson, there is no active reservation found under your name in our database.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for utilising our service.