Being added to webinars without permission

I'm being added to webinars i didn't sign up for by people i don't know.

I don't know how they got my information but i got zoom meeting confirmations and reminders for webinars that I didn't sign up for.

And the organizer is obviously very shady. They use throwaway email addresses as their reply-to email adds. 

It's messing up my calendar cos these webinars are automatically added to my calendar.

Isn't this a privacy and personal data violation? How can I stop this?