I was a cable installer many, many years ago and I understand what you are saying. It might be that the Cablevision installer assumed that the Verizon service was dead and Auntie Maria was the new owner or tenant. Then the Verizon tech comes back, is pissed off that their competitor used his wiring so he puts it back on his service.
Thing is, I had the brains to realize that there might be two tenants and services in that building and would at least check out where the existing wiring went and maybe get out my meter to see if it's still active.
That intelligence is no longer available today plus installers only care about how fast they can complete a job anyway. So if they can reuse wiring it will save them time.
Now, about Cablevision CSRs. I've found them to be the most incompetent people on earth. Apparently that greedy French guy that bought Cablevision from the Dolans is getting his money's worth from moving the call center from the US to whatever third world country it's in now. So whatever they tell you take with a grain of salt.
Filing a complaint with the state PSC does seem to do something. At least you get a call from somebody at Cablevision that is here and speaks English.