Dishonest sales reps and unresponsive unhelpful customer service team

So I had fallen on a few hard months and my bill had started to rack up and I had gotten several late fees added as well. All perfectly understandable. So I decided to contact xfinity about my recent missed payments and I got a representative offering to do a great deal for me where they would upgrade my internet speed, lower my monthly payments, upgrade my equipment, AND (the biggest hook of it all) they would wipe out all past and present account balance so I was basically getting a clean slate, second chance! I was of course blown away and gladly accepted the offer. Well, until I get the next months bill and it's $600+ dollars and I'm being threatened with disconnection and being sent to collections (which in the state of Utah is against the fair debt collection act and is illegal to threaten your customers with adverse actions ie: sending me to collections) They are now telling me that there is no way I was offered a deal like that because they literally cannot just wipe out my due balance and when I was told that the upgrade to my speed would be cheaper I was informed that they simply upgraded me but now I was expected to pay the difference every month for the new higher speed (a $40 difference). And the person handling this matter with me was very rude, unhelpful, and a straight up liar. They told me that they don't keep recordings of their sales calls so there is no way to go back and verify that I had been offered these things. Little did they know it wasn't a phone call I had used the chat feature on their website and had my entire conversation with the sale rep screenshotted so I have the evidence to back everything up. So after a very, very long phone call trying to straighten all of this out, I ask them to connect me with their supervisor and I'm told that the supervisor has already gone home for the day but they will set up a call back so this can all be dealt with as soon as possible. But before letting them go I asked them to please downgrade me as far as possible because I couldn't afford this current bill. Especially since they are at this point still trying to make me pay my old overdue balance as well. They said they did. Well turns out they didn't do that for me either. Needless to say I never recieved the callback.... And My bill is currently over $800 dollars and still stacking because no one is doing what they say they will and the only person getting [Edited: "Language"] in the whole ordeal is me. Xfinity needs to stand by their sales reps promises and the customer service team needs to actually do what they say they will. How hard could it be to modify my current plan and schedule a callback? So I'm still paying the outrageous price per month I didn't agree to and they won't honor ANYTHING I was promised. And like I said, I've got the screenshots to prove everything. This really is unacceptable. At this rate I would never, ever recommend xfinity to any of my friends or family.