There is no technological solution. (The phone system as a whole is just so old).
There is no human solution. (The other company will not bother).
You have three options.
1. Wait until it stops and ignore it
2. Change your phone number
3. Sue Level 3 for damages (and file a police report)
In my professional (but not legal: I am not a lawyer) opinion, there is no way to resolve this sort of problem other than suing the closest legitimate business that links you to the perpetrators. Whoever is furthest downstream to the bad guys is your only target, and suing them is probably the only option. Maybe just to get a C&D, maybe punitively just in hopes of getting them to clean up their act. A police report on its own will have zero effect: the police just don't care about IT crimes on this scale.
Sue them, and as part of it file a police report. Don't even bother with any other options at this point: they are not likely to work.
(Again, not a lawyer, just an IT professional).