rectify inaccurate invoice

How can I get an invoice to show the CORRECT amount due? I was at $75/mo for 24 mo (promo was $85, using autopay reduces by $10). When it went up after my 2 yrs, it almost doubled. I contacted the customer service bot which finally got me to a human (I think?) who promised me it was back at $75. That didn't happen so I turned off autopay. The next month, same thing so I went through the same HOURS of 'fun' again and had the same answer and same inaction.

But now it is $436!??!

For two months that would have been $150 per two agents on two different days.

I'm livid, so I returned my box today and no one in the store can help. I had to sit in front of video screen with someone else who couldn't help. I came home and called customer service, got the supervisor and STILL no one can make this right. The supervisor said since none of their cust serv reps put the order in, I do owe >$400. I repeatedly told her that is THEIR error, not mine. She can see the chat history, she can see that I was told I'd be granted the extended promo TWICE, but since she is 'not the owner of the company, there's nothing she can do'. WHAT!?! All I want to do is see an invoice correctly adjusted to $150 so I can pay it and never have to deal with this crooked organization again. Push autopay and then hike prices hoping we don't notice!? Shame on you. Horrible.