TRACKER DEBIT ORDER PROBLEMS AFTER CONTRACT WAS STOPPED.

I had a tracker installed in 2011, when my insurance company required one. I never received a copy of the agreement. Given the economic conditions and with everything going up in price, I found out from my insurance that the tracker is no longer needed. I stopped the next debit order in March. Tracker sent me a text message , asking me to reply as to why I stopped the debit order. I told them I am cancelling the contract as my insurance does not require one because my vehicle's value has dropped below the threshold for a tracker. The debit orders still continued and I had to reverse them every month. By 26 July I had had enough - they are so clever as they use a different description for each amount they take off, so it is impossible for the bank to refuse the various debit orders with various descriptions. I wrote an email and explained the whole situation. I only got a reply on 3 August where a lady by the name of Lyndle Richards said she can cancel my contract, but I first need to pay the amount in arrears. I asked for a copy of my contract, which I never received - as far as I know one has to supply our client with a copy of the contract per the CPA within 14 days of the date of signing the contract? Needless to say, I am still getting billed - on 26 Oct it was R 630 as well as R945...... I am now GATVOL. How do I stop this? Do I need to change my bank account number, which I have had since 1983???