[ca] Getting A Non-profit To Leave Me Alone After I Professionally Seperated From Them And They Keep Emailing And Calling Me And People I Know?

I did some work for a Non-Profit that runs several trade shows. Logistics and Coordination work, volunteer with limited 'perks' and no wage. Think like, working with corporate partners and ensuring they got the space they bought, things went well for them, follow-ups and etc.

I recently decided to seperate myself from the Non-Profit because I believe they may be doing unethical or illegal things with certain funds they are receiving, and while I'm much too far down the flagpole to matter, it just isn't worth the headache. I notified them of this about 2 months ago, admittedly while we were planning for the next show. I fully admit I left them a bit high and dry here, but I didn't see a way forward that didn't expose me to an unacceptable level of personal and professional risk, and I made the call to cut ties without more than an email 'I will no longer be able to participate, thank you for your time'. As a Volunteer and in no way a paid employee or an officer of the non-profit, I'm not required to do more than that. They had not yet issued me anything of any financial value (show tickets, etc) nor did I accept them.

Unfortunately the organization has taken this very, very poorly. Multiple emails a week from multiple email addresses demanding that I must complete my 'duties' or 'face consequences' for bailing without training someone to take over or passing my workload and workflow knowledge to a successor. This was fine for a while, I'd just mute or block the emails. But they've now started interfering with my actual life by calling known associates of mine and demanding they get in touch with me to talk to the organization, calling my place of work, and even calling family members they likely googled based off my Facebook/Social Media.

Last week I notified them through email that any further communication was unacceptable and that this felt like harassment and that I would like any future communication to be done through the organization's legal counsel. They told me that if I want it to stop I can 'come do my job then' to which I did not reply. They have continued to call people in my life and harass them and myself.

What are my next steps? Can I get a lawyer to send them a notice to stop contacting me directly or indirectly? They're telling people who they contact that "we cannot legally be forced to communicate through a lawyer" and I know that the specific person doing this at the organization is one of those people who thinks he could google a law education and knows better than anyone how the law works, so he's just determined that he can keep doing this.

tldr how the fuck do i get these people to stop harassing me at home, work, friends, family, etc. Blocking phone numbers/emails isn't working and they're just going around it.