I tried to search on Evilution but there are non topic talk about this? Can anyone help me out? With photo please.... if possible.

They are held on with clips at their base. Just pull of. I found pushing laterally to one side and lifting diametrically opposite side works easier. Evilution simply states "pull off heater ball".
http://www.Evilution.co.uk/index.php?id=224

PS. I like the colour of the interior of your Cabrio. Much better than mine which is stream green.