Uverse account billing error

I am trying to get some assistance with a Uverse billing issue. I can canceled my service in early January as my promotional period was ending and I could not afford to pay regular pricing for my Uverse service. I had the service for 2 years and loved it! I just could not pay for the service so I canceled it. i paid my last service bill which was for Dec-Jan 19th and service was canceled. I returned all my equipment and thought I was done. Not quite. I received a bill for Dec- Jan at the regular rate for the Uverse 300 plan. I called ATT and was told it was an error and "not to worry about it" the bill would get reversed out the following month. Well, the following month came and now I receive a late notice.  I called again and was told  to pay the bill ($160+) and then I would be "credited" for the amount on the next months bill. I advised the gentlemen I was not going to pay a bill I did not owe just because Uverse bills a month in advance. He put me on hold and came back and advised me to just pay the portion I owe for the internet and to " not to worry about the rest, it would be taken off" . So now I am getting text messages and emails that I am now past due on the bill. I called back today and was told the same thing, to pay the bill and i would credited back. I informed the young lady that I was not paying a bill I did not owe. I asked to speak to a supervisor and she informed me the bill could not be changed, I would need to pay it and the supervisor was not able to correct it. Yes, I did get loud with the young lady, I apologized to her but let her know I was VERY frustrated.  Without even asking permission to put me on hold, the line went silent. I waited for about 6 minutes and finally was so upset, I hung up. I figured she would call me back because she did ask for my phone number, but three hours later and no phone call. So I have wasted about 3 and half hours total on the phone plus about another hour "chatting" with associates who cannot solve my problem. I have been a customer of ATT since I got my first cell phone, over 20 years and I have to say I am appalled at the service I have received. I "cut the cord" on Uverse but went to Direct TV Now so you are all still getting my money, plus I have my internet and cell phone service with you all. I am hoping this forum can provide some sort of resolution or at the very least, someone who will reach out to me.