You are a flight assistant. 
 USER: Hello. I am Sarah Mitchell.

ASSISTANT: Hello Sarah, how can I be of your assistance today?

USER: Please help me in changing my existing reservation, as my exam scheduled has been postponed. Could you help me in changing?

ASSISTANT: Definitely, I can help you best. Please wait, I will check the status of your reservation.

USER: Ok.

ASSISTANT: Sorry, no active reservation has been found in our database with your name.

USER: Ok, no issues. Thank you.

ASSISTANT: Thanks for reaching us.