You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Joshua Campbell here.

ASSISTANT: How  can I assist you?

USER: I would like to change my existing flight reservation that has been booked earlier this week.Could you please help me in re-modifying my dates in the reservation?

ASSISTANT: Ok, please wait I will check in our records of the active reservation sheet.

USER: Sure.

ASSISTANT: Thank you for waiting. There is no reservation been found on your name in our records. Sorry for the inconveniences.

USER: Thant's fine, thanks for your information.

ASSISTANT: Thank you for connecting our agency.