Poor Service / Cancellation Problems

We have cancelled our Wi-Fi network in November 2017 after having it for more that 5years. I spoke to so many employees and sent my cancellation form and ID to all of them including the cancellations department / service cancellations but they are still deducting. I reversed it at the bank after they deducted and then they made a double deduction the day after. I do not know what to do anymore. I keep on sending them mails that includes my bank statements as well as my cancellation form but I do not get any response. It seems they refuse to cancel my Wi-Fi as they are still deducting.