upstream providers don't care, they will just forward your email to their abuse contact and call it a day, if they do anything at all.
That is fine. By forwarding, they will have proven they received the message, AND the network in question will be more apt to respond in many cases.
At a later stage of the game when you get your lawyers involved their upstream providers will likely respond, for example, it's not worth their while to fight a lawsuit you can file against the upstream provider about their customer's activities.
Years ago I took a new position at a company when I received a phone call from an ISP stating that my servers were port scanning someone who complained. They were going to turn off our network access. Surprised, I looked into it. I discovered they were right. Someone had allowed malware to get installed on several of our systems. After some cleanup work we were good but it left an impression on me. Besides asking a new employer more in depth questions about their security (or lack of it), that ISP's would be a good place to file a complaint when you are port scanned over and over again.
Might be time to contact THEIR ISP and yours. Ask them to block or disconnect them. If anything, once THEY get a phone call about the complaint, it will wake them up a bit