comcast xfinity Comcast ripping off customers Palm beach Florida Nationwide

I am a customer of Comcast less than six months, when I signed in. In January 2016. There was a promotion price of 19.99 a month for a year.
Since then, they change the price once, and in April. They double my price. Or even triple. When I complained to customer service billing department. They told me that I have to sign for direct payment. And they removed all kind of promotions that I was not aware of. I talked to other people and they told me that Comcast is known of doing those kind of ripping off customers by changing prices after you sign been for a special price.