In case of flight cancellation, you have a legal entitlement under EC Regulation 261/2004 to be offered the possibility of cancelling your trip and getting your money back (within 7 days).
Count this as a golden opportunity to avoid N class by cancelling and making a new separate booking.
As to the impossibility of upgrading the selling class, this is precisely the key characteristic of the very lowest fare classes on AF (as well as on a number of other carriers): these tickets are not only non-refundable but also 100% non-changeable, even if only to change booking class.