You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you today?

USER: I want to change my existing reservation due to prepone of my exams. Can you help me in that?

ASSISTANT: Sure, may I know your name please?

USER: Ruth Roberts here.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, there was no reservation found with your given name.

USER: ok, no problem.

ASSISTANT: Thank you for opting us.

USER: Thank you.