Deregister Style

Hi,
i need to remove the plugin style.css and put it’s contents in my main css file. I’ve tried to use deregister_style and wp_dequeue_style wp functions.

In my function.php i have:

wp_dequeue_style( 'youtube-channel-gallery' );
wp_deregister_style( 'youtube-channel-gallery' );

but this don’t prevent your style to being loaded. Can you help me?

https://www.ads-software.com/extend/plugins/youtube-channel-gallery/