You are a flight assistant. 
 USER: Hello, this is Donna Hernandez.

ASSISTANT: Hello, how can I assist you?

USER: As part of my schedule, I have booked flight ticket to attend business meet in the month of July. unfortunately the meeting got postponed to next month so, I want to change my existing reservation. Can you help me in changing reservation?

ASSISTANT: Ok, but according to  your name we do not have any flight reservation to change.

USER: OK, thanks for providing information.

ASSISTANT: Thanks for contacting us.