Bill is significantly higher than "estimated monthly bill" quote

Recently, Xfinity moved my regional sports network to the ultimate tv package.  Since I was in a term contract, I called in to see if I could upgrade my plan without losing the discount.  A customer service rep was able to update my package through an add-on, quoted me a new price, and I accepted and upgraded my package.  I received an email confirmation (which is also available on my account online) with the promised price there in writing as an "estimated monthly bill".  I watched my hockey game that evening and thought everything was great.  A few days later, when I went to watch another game, the channel was blacked out again.  I called again, the rep this time could see that I had ordered the upgraded package earlier that week but also noticed that I was still on my old plan.  She went to fix the problem, I agreed to the upgraded service and was quoted a new price that was actually a few dollars cheaper than what I had heard a few days earlier.  Again, I received the confirmation email with this new price listed in writing.  Then, yesterday, I received my first bill since these changes and it was nearly $100 more than the quoted prices.  After several hours of dealing with customer service on the phone again, I learned that part of the price increase is because the second rep I had spoken to on the phone had forfeited my promotional pricing from the term contract when she upgraded my plan (I specifically asked on the phone that I would not be losing my promotional pricing).  I was told that there are no promotions available for my account and there is nothing they can do.  I would like to either receive my service at the quoted price (or close to it if taxes or fees have shifted slightly), return to my old plan with my discount back intact until the end of the contract, or I will need to cancel my services.  This can not be legal to quote a price and then refuse to honor it.