Collection agencies are a vital part of the capitalist financial apparatus. Banks rely on them to enforce loan term agreements, and in turn defend them when in negotiation with e.g. Apple, when e.g. negotiating agreements regarding e.g. Apple Pay. I suspect (but cannot prove) an elaborate leaning on mobile companies to keep nonconsensual cold calls possible.
Look for this state-of-affairs to change abruptly when being in arrears can directly affect the state of your device.
I expect, by 2025 at the latest, that mobile service and handset providers will begin kneecapping devices whose owners have displeased Equifax. When this occurs, it will no longer be necessary to allow nonconsensual calls, and there will be much touting of the new-and-improved DND.
Probably court summons and legal stuff works similarly, so my second prediction is that, around the same time, it will be possible to serve you notice of a subpoena by unblockable alert.