You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: I would like to shift my planned dates to some other dates, please help me in changing my existing reservation.

ASSISTANT: Ok, I will help you with the modification of reservation, can I know your name?

USER: My name is Nicholas Garcia.

ASSISTANT: Ok, please wait a moment I will check.

USER: Sure, take your time.

ASSISTANT: Sorry as per your request the change of reservation is not possible because no reservation is found on your name to proceed.

USER: Ok, no issues. Thank you for your information.

ASSISTANT: Thank you for choosing our agency.