Muting or blocking does not help. They have you added to a list or something and anytime they send a conference call you get it too. I was dealing with this also ...
I was friends with someone and it turned ugly, so I unfriended and blocked but they still could conference call me. I waited about a year of annoying conference calls and finally tried one last time to get them to take my name off the list. It worked! I suppose they forgot who I was and the argument we had. I gave them 50L just for doing it. Hopefully that will be the end of it. But something needs done about this. W