Time Warner Cable Charging more that their posted price on the internet Internet, North Carolina

I had been using Time Warner Internet service for several years paying $41.95 a month. I got a call from one of their sales reps and she stated they were running very special priced to bundle TV and phone with my internet. She informed me that the price would be $89.99 for all three and stated that there would be no price increases for two year and there is no contract. She also stated that I would be able to watch TV on my PC and mobile devices. Last month I noticed that my bill was higher so I stared to look into it. They stated they are now going to charge me for the modem. I explained that I was told the price was fixed for two years. They stated I have no contract. So now I am really unhappy as they lied to me to get more sales and the TV to PC product of theirs has never worked. I researched and found that you can only add services online, but to cancel a service you had to call them. After waiting on hold for 25 minutes, I explained to a customer service rep that I wanted to cancel the TV portion of my services. He came back and stated that it would now cost me over $100??? I stated to him that their current prices they have on their internet site is $44.95 for internet, $19.95 for phone, and $3.95 for the new modem charge. That adds up to $68.88 so how can they tell me for two services they now want to charge me over $100???  He started giving me some bull about I was an existing customer and the prices were for "New" customers... I asked where is that information posted on their website and he stated it wasn't and I didn't have a contract. So I stated I would cancel all services and then tomorrow go back on line and sign up for their posted prices. He stated I couldn't do that as I had to be a non customer for over 30 days.  How can a big company get by using those unscrupulous business tactics???