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

ASSISTANT: Hello, how can I help you?

USER: My planned trip to Las Vegas with my friends got postponed, So I want to change my existing reservation. Could you help me in changing my existing reservation.

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: We have not found any flight reservation on your given name.

USER: Ok, no issues. Thanks for your service.

ASSISTANT: Thanks for choosing us.