alt Hacker NewsCarriers both land/VoIP and wireless must attest to having fraud mitigation measures; this is the "Robocall Mitigation Database" and in Cape's record they exempt themselves from STIR/SHAKEN attestation but state they have measures to prevent fraudulent calling. (which is required for them to be permitted to operate)
What kind of measures are possible to prevent fraudulent calls when the caller is your anonymous customer? The answer is obviously "none," unless you respond to every complaint by terminating service of the offending customer and hoping they don't come back.
> What kind of measures are possible to prevent fraudulent calls when the caller is your anonymous customer?
Presumably some fairly basic heuristics would be sufficient. Robocalling isn't economically viable if you only get a few calls per subscription. You need to place (I assume) at least thousands of calls per day per subscription for it to even begin to make sense. Any account doing that is going to be blindingly obvious provided you have even 30 minutes worth of logs.
I can already walk into Walmart and purchase a cheap prepaid device with cash. That's pretty close to anonymous.