You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: I am Jack Young want to change my reservation due to prepone of my exams. Can you help me in changing?

ASSISTANT: Sure, please wait for a while.

USER: Ok.

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

USER: Ok, no issues. Thank you for your response.

ASSISTANT: Thank you for opting us.