You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Charles Carter here.

ASSISTANT: How may I help you out?

USER: Suddenly my exams got postponed so please help me out in changing the ticket.

ASSISTANT: Sure, I will help you in changing the ticket.

USER: Thank you.

ASSISTANT: Sorry, there are no reservations found.

USER: That's ok, not a problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you.