ADT, worst security company!

I canceled my service with ADT over a month ago. We made sure to do so by putting it in writing. (21 August) We gave them a months notice as stated in the contract that we signed over 3 years ago. We canceled due to the lack of service from ADT. In fact there was zero service from them. Including times that I pressed my panic button and to tbis day no one pitched up. Anyways, I paid for September month upfront. (Paid the end of August) I got another deduction from ADT end of September. I called customer service. They were arguing with me stating that you pay at the end of the month for the service received. Clearly I was not born yesterday and know that you pay prior for the service that you are meant to receive for the upcoming month. The lovely customer service lady, Jodine, put the phone down on me while I was talking to her. Honestly, I don't know why I wasn't put through to the accounts department in the first place as the lady in the customer service department clearly has zero experience when it comes to accounts and how they work. ADT, you are the biggest *****s. I wonder how many times you have done this to people who have canceled your services. I know of a few in my area. Shocking! Everything that you advertised is false. If anyone is looking for a security company to join, I would seriously think twice about joining ADT. They are such a large company and honestly do not care about their clients at all. They just want to take your money!