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

ASSISTANT: Hello, Charles Mitchell, how can I aid you today?

USER: Unfortunately my exams was postponed so I need to change my reservation, can you please help me to change my reservation?

ASSISTANT: Sure, we are happy to help you. Please wait for sometime, I will check the status and let you know.

USER: Ok.

ASSISTANT: Thanks for your time. Sorry, we did not find any existing reservation based on your name.

USER: No issues.

ASSISTANT: Thanks for availing our service, we hope to serve you again.

USER: Thanks for your kind help.