I'm writing to dispute a final month charge as I canceled my account with in the timeframe.

I'm writing to dispute a final month charge as I canceled my account ( or tried to on 08/11/2023 when I paid off my phones and the billing starts on 8/12 ) 

I have been a customer of ATandT for 13 years and was recently sold an upgraded plan and have had nothing but problems. I called in on the 10th after my phone still did not work the way I was sold. Asked the agent to reset it again so I could test my phones and hopefully get them working. After resetting I tested and still have issues. I decided to switch to another carrier. I set up a new carrier and called ATandT to pay off my phones, put in a transfer request and close our account. So I did this, the agent sent me a text to a website I was told was the payoff site for ATandT. I put in my information and then didn't get a receipt. The agent said one would be emailed to me. I waited and no email so I called later that night and was told by a different agent that it was not a site from ATandT and advised I called my credit card company to put my account on and watch for fraudulent charges. Serious? After talking for a while with no additional information and it was getting late I decided to call back the next morning. The next morning on the 11th I called back to check on payment and close my account. They said no payment was made and asked for my credit card info again so I could pay off the phones and close my account. So I gave the agent my card info, they paid off my phone and sent me a receipt on 08/11/2023. I then asked for the transfer for my numbers and to close my account. Stil lots of back and fourth with my new carrier and ATandT to now I thought everything was finished. I needed to get a copy of the last two ATandT bills so tried to log in and the site said I needed to call in because the account was closed. I called in and after numerous transfers was able to get into my account on a temp access. I noticed that I have a bill for this month now even though I called in before the new billing date started. I asked and was told that ATandT will not prorate on closed account. I'm not asking for that. I'm asking for it to be closed on the day I requested to close it and made the final payment. What type of fraud is ATandT running? Please advise what I need to fo before I take this another avenue. This is not how a business should run or treat a customer of 13 years. Not happy with how this all went down. The agent I last talked to said he agrees with me and saw records of all my calls and said since ATandT closed it not on the org day I called in and 1st paid that I unfortunately was in the new billing. Serious? This seems wrong.