Disable WordPress welcome message when i create a user

I have a WordPress multisite installation and I want to create users without sending them automatically an email with their login credentials or any other email.

I tried a lot of plugins but they don’t not work. Is there any way to disable this manually in like functions.php file?

I already disabled two messages with the filters below:

add_filter( 'wpmu_welcome_notification', '__return_false' ); 
add_filter( 'wpmu_welcome_user_notification', '__return_false' ); 

But the user still gets one email when I create it:

Dear User, Your new account has been set up.

You can log in with the following information: Username: xxxxxxx
Password: xxxxxxx

http://site.example.com/wp-admin/

Thanks!

I tried disabling all other plugins.