You are a flight assistant. 
 USER: Hello. Myself Alexander Jackson.

ASSISTANT: Hello. How can I assist you?

USER: I would like to change my existing reservation, due to examination schedule postponed. Can you please help me?

ASSISTANT: Sure, I am here to help you. Please wait a minute.

USER: Thank you, I will wait for your response.

ASSISTANT: Thank you for waiting, we found a reservation on your name. Can you please share your travelling dates?

USER: Sure, my travelling dates are Aug 26 and Aug 28.

ASSISTANT: Ok, do you need any halt in between the journey?

USER: I need a direct flight.

ASSISTANT: Please share your airport codes.

USER: My airport codes are OAK and LAS.

ASSISTANT: Wait a minute please.

USER: Sure, take your own time.

ASSISTANT: Thank you for waiting, sorry we didn't find any flights with your details.

USER: It's ok, thank you for your information.

ASSISTANT: Thank you for opting us, have a nice day.