Downgrade to Internet Only

Good luck is all I can tell you!  I downgraded back on June 15th, to internet only.  I returned all of my equipment, including the modem.  I have received emails stating that all services have been cancelled except for the internet, and indeed, I have no cable channels now.  However, I have gone through two billing cycles where I've been billed for everything, in fact, my last invoice had an increase on it.  Now I'm receiving past due notices.  I have made at least thirty phone calls over the last six weeks, mostly to be caught up in a circle to only be disconnected without ever reaching a live person.  The three times I've actually reached someone, they've advised me that there's nothing that they can do.  It's notated on my account along with a case number, but no one I've reached can help.  This is the worst company in the world to have to deal with.  Customer service is non existent.