You are a flight assistant. 
 USER: Hi. I am Rebecca Hill.

ASSISTANT: Hello, how may I assist you today?

USER: I want to change an existing reservation due to my exams dates were changed. Can you help me out?

ASSISTANT: Sure, please wait, I will check and get back to you.

USER: Ok.

ASSISTANT: Unfortunately there is no reservation on your name.

USER: Thank you.

ASSISTANT: Thank you so much for choosing me. Have a nice day.