You can buy jigs on aliexpress that hold 128 SIMs and round-Robin across 8 GSM radios.
It’s not all for spam per se. Some countries/providers charge a ton for international incoming calls, so bypassing this by IP and making calls in-provider only saves a lot of $$$ for gray-market connectivity.
And it’s cheaper for setting up of in-bound calls too than a business line.
Aside from increased costs, if the phone system were fixed to give us all the stack from the caller info, we could just block any call from outside the US.
Most of these guys will charge you 10-20% less than bandwidth.com or Twilio will
in return for slightly lower reliability. nCLI means you can't set caller ID because the call is coming over GSM, i.e. a simbox type setup. TDM usually means they are reselling traditional phone lines meant for businesses. If you think this already isn't being used to facilitate scams you'd be wrong: https://globalvoipforum.com/threads/offering-russia-for-fore... (unless by "forex traffic" they mean promoting Interactive Brokers). That's an example I found in 5 seconds. Go on some Facebook groups and you will find people offering grey routes to call America for "Amazon traffic," "bank traffic," "crypto traffic." I never really took the time to investigate what those terms mean but it does not sound good to me.
