How to deal with Xfinity's Shady Business Practices

What is the best way to deal with Xfinity's shady business practices of promising 1 thing and never delivering? How come the rep from the states I spoke to assured me I will have my bill waved out of good faith because my experience for 2 months has been so horrible I am cancelling my service? I should have gotten everything xfinity has promised me in writing over the last 2 months because every person I talk to tells me a different story. [Edited: "Inflammatory"]