Fidelity ADT is a **** (unfair billing)

I terminated my security service with ADT end of October (28-10-2022) through an email (***) after calling and being told to send a mail. In November I paid as I was serving a one month notice and that is according to a contract I signed. In December a debit order was raised and I asked my bank to reverse it and later sent an email to ADT requesting an explanation of the debit order and there was no response. Earlier this month I got a call from attorneys requesting that I pay as I'm owing their client. I would like ADT to give me an explanation of what is it that I owe. It's amazing why ADT claim I have an outstanding fee because on 03/11/2022 (6:59PM), I got a call from an ADT employee calling from ***, he was pleading with me not terminate the contract and I let him know that wouldn't be possible. I understand that the call was an acknowledgement of my termination and my email was received.