If your flight is cancelled, you can either reschedule it or get a full refund. If you wish to reschedule your flight, the airline is obliged to offer you an alternative flight, under equal terms and conditions and as soon as possible, or at a later date that suits you.
If rescheduling your flight is not an option, you can cancel it and get a full refund. The airline is obliged to refund the air ticket in full within 7 days. A refund must be issued for each part of the air ticket, including the used parts if the flight no longer suits the passenger's original travel plan.