My NSI is a personal account on a secure part of NSInternational.com.
To create your own account, go to 'Log in' in the top right corner of the home page and select 'Register'. If you already have a My NS account, you can use the same credentials for My NSI.
Some of the benefits of My NSI are:
Checking and updating your personal details
Reprinting your homeprint tickets
(Information about) cancelling and exchanging
Easily rebooking your favourite journeys
Checking your online booking history of the past 6 months
Managing your international discount and loyalty cards
Subscribing to or unsubscribing from the NS International newsletter