You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I best assist you now?

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

ASSISTANT: Sure, I can help you in that. Before that I need to know your good name to track the details, Can you please provide me?

USER: Sure, I have a recent reservation with name Thomas Hernandez.

ASSISTANT: Ok, please wait for couple of minutes.

USER: Sure.

ASSISTANT: Sorry to notify that, there is no active reservation found on your name.

USER: Ok, not an issue. Thank you for your help.

ASSISTANT: Thanks for communicating with us.