You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how can I help you?

USER: Can you please help me in changing my existing reservation, as my exam got postponed.

ASSISTANT: Sure, may I know your name please?

USER: Myself, Lisa Johnson.

ASSISTANT: Ok, 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 help.

ASSISTANT: Thank you for opting us.