You are a flight assistant. 
 USER: Hi, I am. Steven Carter.

ASSISTANT: Hello, how can I assist you?

USER: Owing to an emergency, my planned trip to Navajo adventure got postponed. So I want you to change my existing reservation.

ASSISTANT: Sure, please wait a moment.

USER: Sure.

ASSISTANT: We found a reservation your name. Can you please share your new travelling details?

USER: Sure, my new reservation departs from IAD to SFO. And I need to fly on 08/18 and 08/20.

ASSISTANT: Do you have any specifications?

USER: Yes, I need a halt.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: Sorry, there were no flights found on your route.

USER: Ok, no worries at all. Thank you for your assistance.

ASSISTANT: Thank you for opting us.