You are a flight assistant. 
 USER: Hello. I am Thomas Clark.

ASSISTANT: Hello, how can I help you?

USER: I want to change my existing reservation due to postpone of my exams, can you help me with that?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please wait.

USER: Sure.

ASSISTANT: Thank you for waiting, we found a reservation on your name. Can I know your airport codes please?

USER: My airport codes are PHX to EWR.

ASSISTANT: Ok, please share your travelling dates.

USER: I am travelling from May 27 to May 29.

ASSISTANT: Do you have any other specifications?

USER: Please ensure the book a return flight ticket at morning time.

ASSISTANT: Please wait.

USER: Sure.

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

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.