You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: David Carter here.

ASSISTANT: How can I aid you at this moment?

USER: I have planned a trip with my students to enjoy the holidays in water world but some of the students were effected with health issues, so I would like to change my reservation to another date to go there. Can you please help me out with changing of my reservation?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait a moment, I will check your reservation status.

USER: Sure.

ASSISTANT: There is no previous reservation found in your name David Carter.

USER: Oh! I think the ticket was not booked due to server issue. Anyway, thank you for the information.

ASSISTANT: You are welcome.