Unable to remove codecs M400

[cloud19]

I’m trying to setup a custom template for the Snom M400. I only want narrow band codecs to be used. I created a custom template and it seems that the dect phones picked it up. (I can see the custom name of the template in the phones list on the PBX). However, if a provision the M400 still all the default codecs appear. I can remove them from the webinterface but after a reboot they are back. Can anyone tell me what I’m doing wrong? Or is it possible to force my preferred codecs in another way?