You can disable auto electric parking brake from the instrument panel. Go to Main Menu > Vehicle parameters > Comfort > Automatic parking brake to disable.
The menu might be a little different on your particular model, so do a little fiddling around if you can't find it.
The deactivation of parking brake is confirmed by the lighting of warning lamp on the instrument panel labelled "AUTO OFF". With the automatic functions deactivated, the application and release of the parking brake are done manually.
