Can't Prevent Theme updates

Hi,

I’ve tried few solutions that I saw about how to prevent WordPress theme update and it just doesn’t work.

The theme I changed is:twentyfourteen

I tried to add to the webconfig:
add_filter( ‘auto_update_theme’, ‘__return_false’ );

later i added:
define( ‘WP_AUTO_UPDATE_CORE’, false );
add_filter( ‘auto_update_theme’, ‘__return_false’ );

Still no solution.
I would love to get your help!