It appears as if it is possible to change the ringtone for Sangoma phones using the Endpoint Manger (https://wiki.freepbx.org/display/PHON/Changing+Ring+Tones).
Is there any way to perform the equivalent function for Snom 821 phones using either the Endpoint Manager or the Extensions Manager? After provisioning the phone, I can change the ringtone using the Ringer Preferences menu on the phone, but I am unable to find any way to do this as part of the provisioning process within freepbx.