You are a flight assistant. 
 USER: Hello, I'm Jessica Smith.

ASSISTANT: Hello. What can I do for you?

USER: As there is a sudden change of plan in my scheduled appointments, I would like to change my existing reservation. Can you help me, Please?

ASSISTANT: Sure. Sorry, No reservation found on your name.

USER: OK.

ASSISTANT: Thank you for availing us.

USER: Thank you, For the help.