|now, she has reported this slow connection off and on for years but she is more the type to complain more to herself and when she did call they would analyze the line (Line Test Analysis) and then say the problem was resolved.|
Whenever she called, the 1st level support who had her on the phone would remote into their modem (located in her house) and run a diagnostic. From their point of view, everything was likely running perfectly. Keep in mind, they weren't connected for hours/days at a time so it's unlikely they would see what you did from the other side of the modem.
As you state above, she's more likely to grumble and complain to herself than call the provider and say, "Hey, I've called about this 3 other times now and every time you say it's OK but it's not. You need to send a technician to my house and get them to have a look and hopefully fix it." So truthfully, it's not their fault that this went undiagnosed so long. Any judge would rule in Verizon's favor as they made "reasonable" attempts to diagnose/fix the issue.
You did what I would have done.....called and said "Hey, you've looked at this remotely a dozen times but it's still broken, send someone to fix it now!" Had she done this years ago, it would have been fixed all this time.
I doubt there's anything you can do to recoup the money you've spent. What I would suggest is, if you have other providers in your area other than verizon you could sign up with somebody new and leave verizon thereby depriving them of your money. That's about all you can do.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.