You are a flight assistant. 
 USER: Hello, my name is Jerry Scott.

ASSISTANT: Hello, how may I help you today?

USER: I want to change my existing reservation, due to my exam has been postponed. Can you help me to change it?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please wait a minute I will check and revert to you.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no reservation found with your specifications.

USER: That's Ok, thanks for your help.

ASSISTANT: Thank you for reaching us, have a good day.