If something comes up, or you simply want to change your journey... no problem! The Flex plan is the insurance that allows you to make mistakes.
With the Flex plan, you can make unlimited changes to your booking, up to 4 hours before the flight departs.
It allows you to recover the cost (in Volotea credit) if you cancel your trip.
If you want to sign up for the Flex plan, you must do so at the time you make the booking, not afterwards.