They don't. The company getting the call just knows who they get it from. The reseller chain can be a dozen companies deep. I've ran companies doing 1B+ calls

They don't. The company getting the call just knows who they get it from. The reseller chain can be a dozen companies deep. I've ran companies doing 1B+ calls a week. Any time there's some sort of complaint from a customer or vendor, we just kick it down the line and say "please verify caller ID xxx is correct". We block it, everyone moves on. No one cares. I tried a few times to get the end user to file a complaint. Vendors and customers would just get annoyed; nothing happened. Even in cases where an AG gets involved and sends out a subpeona, I've never seen anything happen. Hell, even on DHS investigations (like where callers are pretending to be IRS agents), nothing happens. Until the FCC starts getting serious about it, that'll remain the status quo. (Only time I've seen things actually happen is when the request is incidental to another investigation, like "terrorism" or drugs. Why the hell they fwd us any details about the suspect beats me. All over plaintext, too.)