You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Roberts Phillips here.

ASSISTANT: How shall I help you?

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 can help you in ticket modification. Please give me some time.

USER: Thank you. Ok, take your time.

ASSISTANT: There is no reservation found for the user name when I checked in previous booking list.

USER: Oh! I think the ticket was not booked properly while I am booking. Anyway, thank you for the information.

ASSISTANT: It might happen due to some issue, thank you for reaching us. You are welcome.