ADT Security gives bad service

After numerous problems with ADT I cancelled my subscription in January 2018 to end February 2018. The last debit order to go off would be January as I pay in advance as per my contract.

They also advised January would be my last payment. To my surprise they made done another debit order yesterday 26 February and due to me having insufficient funds I was charged a R 100 unpaid fee by my bank.

I have made a few calls to ADT...first call I was advised I pay in arrears which is not true. I asked that cancellations contact me.

I phoned a few times after that to speak to someone in cancellations as i have had no call back and had to explain my story every time again before they would put me through to cancellations and every time my call has been disconnected.

I am angry and upset as this R 100 is the last of my money and my reputation now reflects badly for an unpaid that shouldn't have taken place.

I need urgent help.