You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I support you?

USER: This is Daniel Nelson, my exam got postponed so can you please change my active reservation?

ASSISTANT: Sure, please be on hold.

USER: Sure.

ASSISTANT: We found a reservation in your name. Can I have your journey details please?

USER: My airport codes are from ATL to DEN.

ASSISTANT: Let me know your journey dates?

USER: My planned travel dates are from Nov 18th to Nov 20th.

ASSISTANT: Do you have any preferences?

USER: I want to depart in the afternoon.

ASSISTANT: Sorry, no flights were available at this moment.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for reaching us.