Incompetant and underhanded

In 2002 I took out a contract with Chubb, I decided to cancel in November 2015 - because the contract was becomming ridiculously expensive compared to other security companies, and the price you pay when you first join. Long standing LOYAL customers are not given any benefit - just the year on year increases. I phoned in November 2015 and said I wanted to cancel my contract - only then was it suggested that someone call me back and discuss the price I said no Please cancel. NO ONE said it would not be cancelled. So I stopped the debit order. I installed a new alarm and disconnected their radio with no further contact from Chubb. In Jan 2016 I received a call re the cancelled debit order, I informed the lady that the contract was cancelled and she did not question anything !! Fast forward to March 2016 - I get a call saying I owe R1213 which I dont agree to ! (RESOLVED# ********** 2) and that a contract can not be cancelled over the phone (4 MONTHS LATER) I still dispute this but send the letter they ask for, but disagree that I owe them anything. IN April 2016 I get a "sorry we made a mistake" the amount is R2998 (??) <where did this even come from ?> That I dispute again - and hear nothing more from CHUBB in any way, shape or form. Now out of the blue FEBRUARY 2018 - a debit order goes through my account from a debt collection agency ?? Which I cancelled because I had no idea who they were ..... To get told that it is on the authority of CHUBB ???? Is this even legal ( I intend to find out ) After 14 years to be treated like this just because I decided to change my service provider is outrageous ! Really BAD attitude CHUBB