You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you at this moment?

USER: I am Alexander Phillips, I would like to change my recent reservation because my leaves have been changed, can you help me to change that reservation?

ASSISTANT: Sure, I will help you with that.

USER: Thanks for your quick response.

ASSISTANT: Please wait a moment to check your reservation.

USER: Ok, I will wait for your response.

ASSISTANT: Sorry Alexander Phillips, no reservation has found under your name to change.

USER: It's ok, I think it has been not booked before only, anyways thanks for your valuable information.

ASSISTANT: Thank you for choosing us, have a good day.