About 20 years ago I got escalated to high-tier Comcast support for an issue that turned out to be a little of A, a little of B: Comcast (Might have been @Home, based on the timing) required that your MAC address be whitelisted as part of their onboarding process. Early home routers had a "MAC Address Clone" feature for precisely this reason. At some point, the leased network card got returned to Comcast. Our router continued to work just fine... until about a year later, when the local office put that network card into some other customer's home. We started getting random disconnects in the middle of the day, and it took forever to diagnose, as the other customer was not particularly active with their internet use. Whose fault was it? Ours, for ARP Spoofing? Theirs, for requiring the spoofing?
That makes sense.
When the cable modem issued a DHCP request, the CMTS would have been configured to insert some additional information (a "circuit-id") into the DHCP request as it relayed it to the DHCP server.
The short version is that the "competent tech" looked at the logs from the DHCP server, which would have showed that the "same" cable modem (i.e., MAC address) was physically connected to either 1) two different CMTS boxes or 2) two different interfaces of the same CMTS.
How would one cable modem be physically present in two different locations at the same time? Obviously, it wouldn't.
At that point, either 1) there are two cable modems with the same burned in address or 2) one of the two cable modems is cloning/spoofing its MAC address. Which one of those is more likely?
(If you're interested in the details, try "DHCP Option 82" as your search term.)
For instance: "This might just be a loose cable, can you unplug each end of it, and plug it back in?" invariably elicited an "I've already done that", or a brief pause followed by "okay, there, I did it, do you see it?". Lies, often.
But: "Alright, I want you to try turning the cable around for me, yeah swap it end for end. Sometimes you get a connector that just doesn't fit quite right, but it works the other way around and it's faster than sending a tech to replace it", would often get a startled "Oh! I hadn't thought of that, one moment..." and then the customer actually DOES unplug the thing, and what do you know, they click it in properly this time.
Then one day, she tells me that she tells people to unplug the power cord, cup the end in their hand, and then plug it back in.
Suddenly, I really liked her. It's a genius move that makes them think they've done something obscure, but she really just wanted them to actually check the cable.
Luckily, I already knew how to fix them. I found the job to be a cake walk and quite liked helping people. But I had to listen to people around me fumble through it.
It was frustrating at the time, but my favorite thing that happened was that I was admonished twice for having average call times that were too low. To them, that's a warning that someone is just getting people off the line without fixing their problems.
They monitored calls and they said I'd never received a complaint, but the system would keep flagging me for low call times so I had to artificially raise them. They suggested that I have a conversation with the clients.
I didn't, and I didn't stay there much longer, but it was quite a crazy situation. But I also felt much less pressure to handle calls quickly after that, too, which was nice.
Everything they do is driven by metrics, and their contracts are written around KPIs like maintaining a ludicrously short average time to answer, short handle times, and open/closed ticket ratios. If they do not hit these metrics, then the outsourcing company owes service credits. The incentives do not align with making customers happy and solving their problems. Everything is geared towards deflecting users with self-help options, simple scripts for the agents, and walking the line of hitting those metrics with the fewest number of warm bodies.
It's a pretty hellish business.
For the last several years, I've gotten my mobile service through an MVNO named Ting. On the rare occasion that I've needed to call support, there's no IVR, just a human who typically answers on the second ring. They speak native English, and have never failed to solve my problem either immediately or with one prompt escalation.
They're so jarringly competent I wonder how they still exist, if being obnoxiously incompetent is apparently a business requirement.
The solution could be a priority support tier where you pay upfront for an hour of a real network engineer's time (decently compensated so that he actually cares about solving the problem) and the charge is refunded only if the problem indeed ends up being on the ISP's side. This should self-regulate as anyone wasting the engineers' time for a simple problem they could resolve themselves would pay for that time.