If you hadn't paid the change fee then the flight is not confirmed. It is the same as a travel agent making a booking on a flight and not ticketing the reservation. If they need to clear space, those are the first to go as the payment was not made to fly on that flight. If you want to be truly confirmed, you should pay the change fee in advance. Emirates was already being generous by allowing you to wait up until departure to pay the fee. Try doing that on most other airlines. They will happily charge you a fee to cancel your flight if you have a non-refundable ticket and take another fee to reticket it or even have you buy a whole new ticket.