You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Rebecca King. I am an emergency. Please change my existing reservation that has been booked earlier this week.

ASSISTANT: Sure Rebecca, please hold on for a moment.

USER: Ok, please make it fast.

ASSISTANT: Sorry, I was unable to find your reservation in our portal.

USER: How is it possible when I had already reserved a ticket?

ASSISTANT: You are right but please check if someone had already changed your reservation. That could be the reason why it is not showing in our portal.

USER: Ok, I will check and get back to you.

ASSISTANT: Sure Rebecca, please feel comfortable to get back to us.

USER: Thank you.

ASSISTANT: Thank you and have a good day.