You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, May I know what kind of service you are looking for?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, I can help you in that. May I know your good name please to track the details?

USER: I am Thomas Carter.

ASSISTANT: Ok, There is a reservation found on your name, to proceed further I need to know your airport codes?

USER: My airport codes are BOS and LAS.

ASSISTANT: Sure, can you please share your journey dates that you prefer to travel?

USER: I prefer to travel on Feb 15 and Feb 17.

ASSISTANT: Do you need any lay by in between journey?

USER: I prefer to travel in a connecting flight.

ASSISTANT: Is there any other specifications regarding your journey?

USER: No.

ASSISTANT: Please be on hold for sometime to check the suitable flight for your journey.

USER: Sure.

ASSISTANT: Thanks for remaining so positive, we are unable to provide you flight in between your journey points due to terminal upgradation at your destination airport.

USER: Ok, no problem.

ASSISTANT: Thanks for communicating with us, have a great day.

USER: Thank you for your information.