How to safely delete media.net manager plugin in WordPress

I don’t want this plugin anymore or media.net ads on my site it completely slowed it down and I’ve had enough.
I’ve removed all ad placements but when I go to delete the plugin it says can’t delete still active on the main site, when it’s not I’ve removed all ads and they are not showing up and my speed is back to nearly A. Please can anyone help?

Thanks in advance.