You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Margaret Lopez here.

ASSISTANT: Can I know your concern?

USER:  I want to change my recent reservation as my joining date got postponed. Can you help me in changing?

ASSISTANT: Ok, please let me know your name to check the records of reservation.

USER: Above mentioned.

ASSISTANT: Sure, I will check please wait.

USER: Ok.

ASSISTANT: Thank you for waiting, sorry as per your concern I can not amend because there is no reservation been found on your name.

USER: That's ok, thank you.

ASSISTANT: Ok, thank you for choosing our agency.