You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Helen Walker.

ASSISTANT: How may I help you?

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

ASSISTANT: Sure, I am happy to help you to change the ticket details. Can you please give me a minute?

USER: Ok.

ASSISTANT: Sorry to intimate you that, I have not found any active reservation with your name to change the details.

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

ASSISTANT: You are welcome. Thank you for reaching us.