I really need help. Xfinity has my account & billing completely screwed up.

My account and billing is all screwed up and wrong and has been for 2 months now and I keep trying to get it fixed but haven't been able to and the its gotten way worse from one month to the next. This is what has happened (sorry for long post but I don't know how else to explain. TIA of anything can help or have advice what to do)

On July 1st I contacted Xfinity about a new plan/deal for Internet service. I've had Xfinity Internet for almost 4 years but no longer had a contract or special deal. I took a new plan and 2 year contract. Instead of getting the good deal I was offered and agreed to my account & billing has been screwed up ever since and is worse each time. I've repeatedly contacted Xfinity & have spent hours, multiple days, multiple people but they've done nothing to fix it and it's only gotten worse. The latest time it was supposed to be escalated to somewhere higher up & was told I would get an email response within 48 hrs followed by contacted by phone. I got nothing. The deal I took was to be for 800 mbps internet speed + rented modem + unlimited data all included at $50.00 then down to $45/mon w/auto pay. Instead the following has happened. When I got my next bill Iafter changing to that plan was wrong (billing me more than it should be). I contacted Xfinity after being on the chat for a long time with one of their agents and told them the problem & they looked up my account and when I previously contacted Xfinity and was offered & took that plan /deal and ended up getting the following response. "I've checked your account details and found that you're absolutely correct. Previously, you were told about 800 mbps internet speed + rented modem + unlimited data at $50.00 if you enroll for auto pay then it gets down to $45/mon Due to some technical issue, deal charges are not getting reflecting correctly. There is no need to worry at all. I'll go ahead and take the ownership of this situation. I'll submit the dispute for the deal so that it can be corrected and going forward, you get the monthly bill based on stated monthly pricing of $45.00 with auto pay discount." That was on July 21st I even have screenshots of this and of when I was offered & took the new plan/contract. I also have an order Id # from that. I was told I would get a bill credit for that bill & was assured that it would be fixed going forward for future months months billing. After that at first I thought the problem was taken care. 2 days after that my account was showing I received a credit adjustment & now was showing $101 credited to my Xfinity account (this should have payed the next 2 months payments August & September) I thought it was ok now, but then the next moth I get my bill statement and its screwed up even worse. The money they credited to my account has disappeared, is not on my account and wasn't used to pay the bill either. And It's currently saying I owe past due $100.26 (a few days ago ot said $140.26) this is wrong I owe nothing past due. I have never missed a payment or payed late and its on automatic payment. Its also saying that I owe an upcoming $140.26 on September 11 (as an automatic payment) this is also wrong. I'm only supposed to owe $45 on September 11 (and each month, Since changing to a new plan 2 year contract on July 1st.) The last time I contacted them on the morning on August 29 and was on the chat a very long time with 2 different people it was supposed to be escalated to somewhere higher up & was told I would get an email response within 48 hrs followed by contacted by phone. I got nothing.

How can I get this fixed? I really need this fixed & permanently fixed, not where its back to being all screwed up again the next month. I really need help, this is a huge problem for me & I need it fixed & Xfinity won't do anything to fix it. I have tried repeatedly multiple times multiple people for 2 months now & ots only gotten worse. I have screenshots from the chats with the Xfinity agent & an email & order ID to prove what I'm supposed to be paying. But I still can't get anywhere with Xfinity to fix the problem. Is anyone else having this problem? Does anyone have anyway to get it fixed? Its all completly unacceptable on Xfinitys part. And I really need help don't know how to make them correct it, I've done nothing wrong but am getting completely screwed.