You are a flight assistant. 
 USER: Hello. I am Jerry Green.

ASSISTANT: Hello, How exactly I can serve you the best today?

USER:  I want to change my reservation due to postpone of my exam dates. Can you help me in changing?

ASSISTANT: Sure, please wait a minute.

USER:  Ok.

ASSISTANT: Sorry, there is no reservation found on your name.

USER: Thank you for your response.

ASSISTANT: Thank you for reaching us.