[Help]: Error when styling plugin [ call_user_func_array() expects parameter … ]

Hey Guys,
 
When I try to style the plugin following the instructions found here: http://www.designwall.com/guide/dw-question-answer-plugin/ I get this warning: 
 
Warning: call_user_func_array() expects parameter 1 to be a valid callback, function ‘dwqa_new-theme_scripts’ not found or invalid function name in/Applications/MAMP/htdocs/wordpress/wp-includes/plugin.php on line 505
When using this code the the instructions say: 
 
Note: Please change ’simplex’ to your theme name.
 
so i changed them all and then made the code this: 

/* load style for DW Q&A plugin */
if( !function_exists('dwqa_new-theme_scripts') ){
    function dwqa_new-theme_scripts(){
        wp_enqueue_style( 'dw-new-theme-qa', get_stylesheet_directory_uri() . '/dwqa-templates/style.css' );
    }
    add_action( 'wp_enqueue_scripts', 'dwqa_new-theme_scripts' );
}

Have I done something wrong?