In terms of how you, as a private individual, can "make them stop", there's little you can do, and it sounds like you've already tried.
On the question of who (possibly) could, it will depend on jurisdiction. In the EU, you would be covered by GDPR, and could refer a complaint to your national or regional regulator - for example the UK Information Commissioner's Office (https://ico.org.uk/make-a-complaint/).
Since you mention Juno, I would guess you're in the US. It's not quite as simple, but this article https://iapp.org/news/a/america-doesnt-have-a-national-data-protection-authority-think-again/ might give you some useful ideas.
It's not a perfect system, and if the organisation sending the spam is in another jurisdiction things could be tricky, but making a complaint is still worth doing - if your regulator isn't able to do anything, your complaint will draw that to their attention and may lead to protection for others in a similar position.
There might also be a possibility of Civil Legal Action if you can show damages, though I'm not a lawyer so you would need to talk to one to see if this is a possibility.
Otherwise, the suggestions of how you can block or avoid particular senders would be worth following - but bear in mind that if you're intending to take the Regulator or Civil Action route, the more information you have, the better the evidence against them.