Unscrew the two phillips head screws on the back of the seat back. These hold the plastic netting trim into place.

Once the screws are removed, the plastic trim is still retained by a system of clips. To loosen the clips, slide the trim "up" to relieve all but the two bottom center clips, then left/right to relieve the bottom center clips. At this point, the plastic trim is free of the seat back.

Now, remove the old bungee from its retaining clips. It should come out quite easily. Remove the old bungee from the seat back netting.