"Upgraded" to 2 GB not getting it and now phone tech support made it worse

Hello there, So, in the midst of having password resets being forced upon me for months now, and maybe finally getting that fixed, last weekend at the store I upgraded to the 2GB down, 250 Mbps up service. So far after a modem reboot I did go from around 600Mbps down and 24 up to around 700 down and 40 up, which is still not the sold speed. There was a notification that maintenance was scheduled 8/25, then postponed until 8/29. I waited to see if perhaps the maintenance would increase the speed; Comcast had been working to upgrade the plant recently. Since I was still getting the lesser speeds, I called Comcast this morning, against my better judgement. Starting the call with "Angie" at 10:58 am, she broke something so that now I might get up to around 700 Mbps down, but am now only getting 6Mbps up. SIX! She after almost an hour, was getting a "supervisor" but after almost TEN MINUTES of waiting I said "You won" and drove the 30 mins. to my local Comcast store. They checked the provisioning which they said looked correct, and also gave me a new ethernet cable, because I thought maybe the older one that is Cat 5 may not be able to pass the newer speeds, and he gave me one he said was also Cat 5, but upon looking at the label on the wire clearly states Cat 6, but has made no difference. So, I called back, again against my better judgement, but what else am I supposed to do? Spoke to someone else and asked again this time immediately, for a supervisor or at least a Tier 2 tech rep, but NO, after promising he was getting a supervisor he pawned me off to RETENTION. That rep again had me explaining the situation now for the like FOURTH time, and tried to help, while also trying to "save" me even though I had not threatened cancellation... yet. Why waste both our time? He gave me a ticket number and promised a technical dept. supervisor would call me within 5-10 mins. 5 mins. later I did receive a call, from a tech rep, NOT a supervisor, who's phone promptly stopped working, dropping off, coming back for a second long enough to tell me he's having "audio" problems, then after a couple minutes of this *poof* either dropped the call or actually hung up on me, and I've yet to hear back, you know like their supposed to do if the call gets dropped.

Now I'm in the position of having done all t/s steps, including multiple modem reboots and replacing the ethernet cord, after spending HOURS with Comcast reps, driving to and from the store, all of it, on my day off on one of the very few actual 3 day weekends afforded me in my present job. 

All this aggravation because I simply want what I'm now paying for. I really didn't even want to upgrade, not because it's a bad deal considering I'm paying almost as much on a 500Mbps plan 'cuz it's old, but only didn't want to do it because I knew it would cause problems, and lo and behold. Also, only after Angie did something that forced a modem reset, the support page within my account tells me that suddenly now "We've detected an issue with your modem Let's Fix It" which the Fix It is a link that "scans" something and does absolutely nothing except leave the same warning up when it completes. She also kept asking me to do a speed test on my phone because wi-fi; I kept telling her it's not the wi-fi it's the WIRED connection. She also tried to then blame my modem as it's "not compatible", which is a blatant lie, and I have no idea why any rep would attempt such a thing, considering all one has to do is look the modem up and the specs are right there.

My cable modem is a Netgear CAX-80 that with Docsis 3.1 can get up to 10GB down, and allegedly 6GB wireless. I've a Dell XPS 8950 desktop hardwired to the modem in the proper high speed ethernet ports.

There is much more I could type here about the extreme lack of competent customer service, and I write again here, I never blame the reps, it is always management's fault. They provide lackluster training, don't provide the necessary tools, and usually only want "problem" customers to get off the phone and go away, rather than trying to actually get problems fixed. 

Well, including this forum post I've spent over 4 HOURS to have not only the problem not fixed, but it's now worse. How does Comcast stay in business?