You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you at this moment?

USER: I am Joshua Williams. Could you please help me with changing my existing reservation due to postpone of my exams?

ASSISTANT: Sure, I am happy to help you with that. Please give me a moment to check it.

USER: Sure, I will wait for your response.

ASSISTANT: Thank you for waiting, as per your request I have checked in our portal but it is showing that there is no reservation found for the user name in our list.

USER: No worries, I think the  reservation was not done properly.

ASSISTANT: It might be happened.

USER: Thank you for the information provided.

ASSISTANT: You are most welcome and thank you for approaching us. Have a nice day.