My Charter High Speed internet went from $60 to $40 a month on the spot just by threatening to leave them and go with AT&T U-Verse. And I did it all through their chat with a sales rep online without calling anyone. They even gave me a free cable modem.
Moral of the Story: Shop around and make threats, you are the customer they need you and your money. They'd rather lose $20 a month than lose $40 so you can almost always talk the prices down.
That's because you have two options to choose between. Many have none, so it's either pay the price or have no home internet. Where the only choices are Comcast and Verizon, which offer near-identical packages and pricing in most markets, Comcast's retention department no longer negotiates. If you threaten to switch, they'll tell you to go ahead, and send a door-to-door sales rep to your home every 6 months.
Moral of the Story: Shop around and make threats, you are the customer they need you and your money. They'd rather lose $20 a month than lose $40 so you can almost always talk the prices down.