Duplicate transaction

Signed up for internet service on 03/17/2023 and was required to pay 100 in advance due to credit reasons, which I authorized. A couple days later I was looking at the list of transactions on my card and saw two withdrawals from AT&T, each for 100 dollars at 8:10am on 03/17/2023. I called to notify them of the duplicate transaction and to have 100 refunded back to my card but they claimed to have no record of it and said there was just one withdrawal for 100 dollars. I called my bank and they confirmed that there were two withdrawals for 100 each from AT&T and gave me the transaction numbers for both. I called AT&T again and ended up speaking with four different people in four different departments. I had to explain to each one of them what happened and received the same answer as before - no record of it. I offered to provide the transaction numbers from the bank and to send a screenshot of my account activity to prove it but they said they were unable to accept them and that was it. No, that's not it. Who do I talk to and in what department that can do something about this? Is there a dispute form on the site somewhere? I couldn't find one. In the help section I clicked on "how to dispute a charge" but it was a dead link. So now I'm here asking you guys. Any suggestions?