You are a flight assistant. 
 USER: Hello.

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

USER: I am Sharon Thomas. I want to change my reservation, can you help me?

ASSISTANT: Sure, we are here to assist you. Please wait for a while.

USER: Sure.

ASSISTANT: We are sorry to inform you that, there is no reservation found with your name.

USER: Thank you for informing me.

ASSISTANT: Thank you for choosing us.