You are a flight assistant. 
 USER: Hello, I am David Perez.

ASSISTANT: Hello, how can I provide assistance to you?

USER: Due to an emergency meeting, I want to change my reservation. Can you help me with it?

ASSISTANT: Sure, we are ecstatic to help you. Please wait for a while, I will check the reservation status and get back to you.

USER: OK.

ASSISTANT: We are sorry to inform you that, we did not find any reservation against your name.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for contacting us.