I have been billed incorrectly for 2 years

This has gotten beyond a nightmare now. After paying ~$70- $80 a month for Internet 50 mb service, I called customer support for the 6th time and finally got thru with someone that could help. He was kind enough to understand what was happening and how I've overpaid for so long. He reduced the bill to around $45 a month. We also have a phone service that we've NEVER used once, the only reason we got it was because ATT told us that was the only way to get a cheaper internet service (which turns out to be a lie). 

Around this time, our ATT internet modem just stopped working all of a sudden. So we called ATT and the technician did some tests and it showed that the internet modem was indeed faulty and that it wasn't our fault, so they would replace it for free. Few days later a new modem arrived, which was wonderful. Now I had to also package the old modem and drive to the post office and wait in line and send it back to them. My time is valuable and I'm a busy person, so finally I went to the post office to get this done. Before you know it, I got a non return item bill of $150 + 15 tax and a few other fees totaling ~$170.

So again I have to call ATT to see what is the issue, wait 10 minutes to finally connect. An agent tells me that that bill will nullified soon, because I've sent back the modem, it just takes some time for them to process it. She also told me that I don't have to pay it and that it would get deducted.

So I make sure she makes a note of that under my account and that I wouldn't get late fees for not paying something that I shouldn't owe. And it turns out, I did start to get late fees and when they finally took off the non-return item fee, they never took off the late fee.

So now I have to call in again to get that taken care of. Finally an agent said he will credit me $24 for their problem, this was a few weeks ago. Right now it still hasn't been taken care of.

Wait there is still more issues. For about 6-7 months, we were also getting billed $10 for some DirectTV charge. We dont have directTV. It was told to us that if we get this service, our ATT bill would be less. It was less for 1 month than it went back to the old price. And the $10 just continued to charge for months.

So overall, how much time and money and emotional strain has this cost me? I don't know. It just took me 1 hour to draft this email. I've had to call ATT over 30 times to fix issues.

So I hope since this is an ATT forum, someone at ATT can fix my issues once and for all, and give me back all the $ that's been wrongfully charged, and the fees and late fees that have been charged to me because of wrongful charges in the 1st place.

If I knew it was going to get this bad with ATT, I would have obviously not gotten their service. And also just got the regular full price internet and not worry about trying to save $10 or something.