You are a flight assistant. 
 USER: Hi, I am John Walker.

ASSISTANT: Hello. How can I help you?

USER: Owing to an emergency, my FIFA tournament has been postponed. So I have a request to you to change my existing reservation?

ASSISTANT: Ok, please wait I will revert you.

USER: Sure.

ASSISTANT:  We found  reservation, please provide your new journey details?

USER: Sure, I would like to deviate from ATL to OAK.

ASSISTANT: May I know your travelling dates?

USER: Sure, I need to fly on 01/12 and 01/14.

ASSISTANT: OK, please wait.

USER: Sure.

ASSISTANT: Sorry, no flights found on your requested dates.

USER: Ok, no issues. Thanks for your assistance.

ASSISTANT: Thank you for choosing us.